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View Full Version : Exhaust manifolds are RED HOT and 2k idle!



Scott Long
08-08-2003, 06:09 PM
I just finished putting my engine together after changing the head gaskets.

I started it up and it runs good no check engine lights, but it had a vac leak and would barely stay running. So I fixed the vac leak at the tubes and top, it runs now but only about 10" of vac. I still have a vac leak somewhere because I can hear it whistling.

The first problem is the car wants to idle at 2000 rpm. I just pulled off the TPS and inspected it, reinstalled it, and it makes no difference. I even unplug it and the car idles higher. Maybe this sensor is bad? What would cause a car to idle at 2000 rpm? The throttle cable is adjusted fine.

Second problem the car gets hot after only a few minutes of running. I looked and the exhaust manifolds are glowing red hot both sides of the engine, and the resonator was damn near glowing. The cats are off this car but it still has the factory resonator and mufflers. There is air blowing out of the tail pipes so I know its not plugged. Also it's not blowing any smoke of any kind thank god. I want to get it to run cooler before it pops the head gaskets again. I have a 160 degree t-stat in it but I'm going to take it out since I think it might be sticking. I also am going to replace the radiator cap even though this one is brand new 16 lbs pressure release.

Also when I rev it up its smooth until it goes into boost. The plugs and wires are new and I just traced them back to make sure they aren't crossed at the coil.

MIKE 38sc
08-08-2003, 06:20 PM
That motor is running lean because of a big vac leak. Once you get the vac leaks fixed and if it still idles that high check the AIC on the throttle body. Hard to give anymore info till you get all vac leaks stopped.

Scott Long
08-08-2003, 08:02 PM
Ok the IAC is fine, I cleaned it while I had the motor apart. I think the vac leak is coming from behind the blower, I'll have to take it back apart and check.

Now this pisses me off. I pulled out the T-Stat and am running w/o it right now, within 2 minutes of running the temp gauge goes past red and the manifolds are glowing, we shut the car off.

I might also bypass the heater core when I pull the blower off incase its clogged. Any suggestions as to why the car runs so damn hot? I'll pull the plugs later or tomorrow when it cools down to double check and make sure I'm not dealing with leaking head gaskets but I torqued them down spec according to the FORD shop manual.

silversc90
08-08-2003, 08:08 PM
check for coolant flow , maybe the radiator needs rodded?

SDbird
08-08-2003, 08:39 PM
it might be your timing is off

racecougar
08-08-2003, 08:48 PM
It sounds like the whole source of your problems is not due to the cooling system, but rather due to a large vacuum leak. That would account for the engine idling high, running hot, and extremely high exhaust temps. The vacuum leak is allowing a lot of unmetered air into the engine, which is causing it to run extremely lean (and extremely hot) with a high idle. Fix the vacuum leak, and I'll bet your problems disappear.

-Rod

MIKE 38sc
08-08-2003, 10:29 PM
I'm with Rod on this one. Better find those leaks fast and dont run that engine till the manifolds are glowing or you are gonna need another set of headgaskets and possably a set of heads as well.

Scott Long
08-08-2003, 11:22 PM
Ok, I checked all the IC connections, and vac lines and nothing is leaking. It might be leaking where the return adaptor connects to the intake manifold. Also when we put the intake manifold on we used permatex blue gasket maker instead of the cork end pieces. I don't know for sure if it would leak there or not but its possible. I just really don't want to tear this engine down again.

I didn't know a vac leak would make it run that hot.

MIKE 38sc
08-08-2003, 11:30 PM
Sure it can! Lean mixtures=more heat. Extremely lean mixtures=MELTDOWN. Have you shot propane around ALL joints in the intake system. Are you sure that NO vac hoses are disconnected? If your manifolds are that hot imagine what the poor exhaust valves are going through.
Its gonna be a big leak or a group of smaller ones at once to make your engine idle up that high and get that hot so quick.
Be carefull or your gonna scrap that engine.
How did you check for leaks?

Scott Long
08-09-2003, 12:24 AM
I just did a visual inspection of all the vacuum hoses to make sure they weren't cracked. I also don't hear the hissing coming from any of the hose connections but I can hear it along the back side of the engine which is why I'm thinking its something to do with the rear of the intake manifold or the supercharger where the plenums connect. But I remember tightening everything down and using all the gaskets that came in the set.

Also I numbered all my vac hoses and they all went back to the right numbered connection.

MIKE 38sc
08-09-2003, 12:33 AM
Well if youre 100% sure none of the intake system(meaning every joint between the intake valves all the way through the system back to the throttlebody) is leaking, then yes the manifold ends could be a possability.
Shoot some propane back there and see if it affect the idle speed.

Scott Long
08-09-2003, 01:20 AM
I'm 95% sure the intake system is sealed up. I'll try getting a miniature propane tank tomorrow and try it before the engine gets hot. I swear within about 4 minutes the manifolds are glowing.

I might just take the supercharger off the car again tomorrow and check to see if its all sealed up good. I hope its just this and that the block or heater core isn't plugged. My next try was going to be bypassing the heater core. But that wouldn't take care of my high idle. I know its a leak somewhere cuz I can hear it whistling quite loud.

MIKE 38sc
08-09-2003, 01:33 AM
Dont make extra work for yourself right now by removing anything. Just get the propane and test every joint in the system, you'll find it.
Since it heats up so quick only do as many joints as you test in about 60 seconds.Shut down the engine and let things cool down,then start it back up and test some more. DO NOT get the manifolds glowing again. DO NOT spray propane with the manifolds glowing either.
Once you find the leak then you will know what to take off to fix it.
Dont complicate things by removing and reinstalling parts until you check for the leak.

racecougar
08-09-2003, 01:41 AM
Originally posted by MIKE 38sc
Dont make extra work for yourself right now by removing anything. Just get the propane and test every joint in the system, you'll find it.


Exactly. Like I said earlier, I really think that the vacuum leak is the source of your problems. It can definitely cause all of those symptoms.

As far as your cooling system is concerned, a 160 degree thermostat is probably a bit too cool. The radiator may have trouble cooling the coolant if the thermostat is constantly open.

But that's not your main problem, so don't mess with that yet! Fix the vacuum leak, then if the car is still running warmer than you like, start messing with the cooling system. The first thing I would recommend is installing an aftermarket gauge. The factory gauge really doesn't tell you anything at all (no actual temperature reading, since there aren't any numbers on the gauge). My splitport tbird overheated with the factory gauge at "N" of "NORMAL", which was evidently a little warmer than normal operating temps.

-Rod

Scott Long
08-09-2003, 01:28 PM
I'm just hoping my head gaskets didn't get damaged by letting it get that hot. It's not smoking so I'll take that as a good sign. I hope these fel-pro gaskets are as good as they claim. I'd be pissed if I melted the fire rings in the gasket.

I am gonna pull the wiper cowl off so I can get down by the back of the blower w/ the propane. I'll let you guys know what I find.

What will it do when I find the leak? Rev up, or idle down?

MIKE 38sc
08-09-2003, 01:40 PM
Thats gonna depend on how bad the leak is, sounds like you got a bad one. Once you apply the propane to a joint if the idle goes up or down you have found 1 leak, but check everything you could have more than 1.

XxSlowpokexX
08-09-2003, 04:08 PM
are you using stock heads and a stock manifold or hav eyou had porting work done at all...Maybe something was milled off...If it appears all your connections are sealed probperly it is possable teh lower intake isnt seating properly to intake ports...Definately soudsliek an intake leak..The silicone on the ends wouldnt be teh problem..What cam do you have??....Some regrids do give you around 10inches at idle

Scott Long
08-09-2003, 09:44 PM
Damon, the cam is stock. I had the heads milled and ported and polished on the exhaust side only. The manifolds have been painted with 1200 degree Aluminum Silver paint but they are stock. The cats have been removed but the factory exhaust is still under there till I get it running right and to the exhaust shop.

The mods are: 190 lph fuel pump, 70mm MAF, K&N filter, a/s removed, vac caps on the SC crosstalk hose connections (not leaking there), and a trans-go shift kit, plus the ported heads.

I did bypass the throttle body coolant lines that early SC's have. From the metal coolant lines that run to and from the heater core there were two smaller connections that go into the throttle body. I took a piece of hose and connected them from one side of the engine to the other. So the throttle body now has no coolant flowing through it to heat it up. I don't know if it will help any or not, but now I can change the TB without having to figure this out later. I know some of the LT-1 guys talk about the throttle body bypass so I did it on my car.

MIKE 38sc
08-10-2003, 12:58 PM
Scott how much was removed when you got your heads milled?

Scott Long
08-10-2003, 01:00 PM
Mike, the heads were only milled .005" since they weren't warped at all. The car had high mileage and the gaskets blew one night at the beginning of winter. The motor was real clean coming apart, no bolts broke, pistons looked good except for a little carbon build up which I removed.

MIKE 38sc
08-10-2003, 01:06 PM
Well .005 shouldnt cause you to have to have the intake milled.
What did you find out with the propane test?

Scott Long
08-10-2003, 05:11 PM
I'm still trying to clean out the garage so I can get my girlfriends cavalier inside so I can do some trans/body/suspension work on it. But I'm going to get a tank of propane today and try the leak test so I'll be back shortly w/ results.

Scott Long
08-10-2003, 11:46 PM
Well I got a propane torch kit today but I was busy putting in a 160 degree t-stat in my 92 SC and wiring up a system in my friends Sonoma so I'll have to test it tomorrow.

A friend stopped by and pulled off the upper radiator hose and sprayed water through it and he said in a matter of seconds it was flowing out of the radiator. He thinks my block is plugged and its not a vac leak causing my problems. Do you think this is an accurate test?

BARTHWY59
08-11-2003, 12:21 AM
nooo that is not an accurate test for your problem... an overheating engine does not have red exhaust manifolds... you have a lean condition causing the exhaust to be super heated..go drain all the water out of your friends car.. start it up ..the manifolds will not glow in 4 minutes..

Rob Noth
08-11-2003, 12:36 AM
If your manifolds are glowing, then as was already mentioned you are running way lean. If you don't have a check engine light ("system at adaptive rich limit") then the system thinks everything is OK, which most likely means... your O2 sensors are bad. This is typical for a blown headgasket - even a slight amount of coolant in your exhaust will ruin the O2 sensors.

As for the high idle, I would start by checking two things. First, look in the TB and make sure the throttle plate is closing fully. Then, start the car and unplug the idle air solenoid (next to the TP sensor on the TB), and see if that fixes the high idle problem.

Scott Long
08-11-2003, 04:37 PM
Ok in a hurry to start up my car, I just reinstalled the old O2 sensors but they didn't give me a CE light.

Also I've unplugged the IAC and it makes no difference. I also unplug the TPS and if revs higher. The throttle plate is fully closed.

MIKE 38sc
08-11-2003, 07:51 PM
Scott...........Look for the vac leaks, its alot easier job to do than going about it like you are. You have vac leaks I promise you. Eliminate that possability first.

racecougar
08-12-2003, 12:40 AM
Originally posted by MIKE 38sc
Scott...........Look for the vac leaks, its alot easier job to do than going about it like you are. You have vac leaks I promise you. Eliminate that possability first.

I agree completely, until you find and fix the vacuum leak(s), you're pretty much wasting time messing with the sensors.

-Rod

markadeck
08-12-2003, 07:10 AM
I am an old drag racer and engine builder from back in the old days. A fairly successful one, my car was once featured in Super Stock and Drag Illustrated. I may not know much about AOD's, in fact I know zero about them. ABS's make me dizzy and I find all this very trick, very effective technology in todays cars beyond my comprehension. But after reading the very first post in this thread I knew this was a vacumn leak, and a big one at that. I sure hope you have not damaged anything by letting any of the exhaust system reach glowing conditions. Don't hold your breath though. Why would you let a friend fool with the cooling system. How can a clog in the cooling system cause the idle to run so high? This guy may be a pal, but he needs to be kept away from your SC.

Les Borda
08-12-2003, 07:53 AM
Scott if you don't have easy access to propnae use brake cleaner in an aerosal can or throttle body cleaner to check for vacuum leaks. If you are hearing it behind the supercharger it may very well be the return plenum gasket area that is leaking. I had the same problem when we put my engine back together, rough idle, low vacuum on the boost gauge(no glowing manifolds though).

Use copper RTV even though it is a new gasket, we tool mine apart, RTV'd the gasket, end of problem.

Good luck

Scott Long
08-12-2003, 07:42 PM
Thanks for the suggestions guys. I really want to throw a new set of O2 sensors in this car though. Maybe its telling the computer to lean out the mixture and that plus the vac leak is causing an extremely lean condition?

Time to play with some propane.

MIKE 38sc
08-12-2003, 09:25 PM
Scott... I'll try 1 more time.
SENSORS are NOT causing this problem! There is NOTHING built into that computer system to cause it to adjust it that lean. The comp is built to work exactly opposite of that.
I dont understand Scott. Why are you so willing to spend hours changing sensors when all you have to do is spend MAYBE 10 minutes shooting propane at the intake joints.
I dont get it.:confused:

markadeck
08-12-2003, 11:43 PM
I get it, it is called DENIAL.....it is a plain and simple bad vacumn leak that must be a real pain in the arse to get at. I can understand it, after just putting a fresh motor in and have to tear it apart must be gut wrenching. But that is what it is gonna take.

wezar
08-13-2003, 12:07 AM
Like I said in my plug for Tbird88's gasket set. My intercooler tubes have been off once and sealed up perfectly the second time . I had 20 inches of vacuum with a small cam in the car.

Sadly my lifter preload is still wrong and I will be replacing my intake gasket set and reusing my teflon gaskets for the third time. For good measure I am changing header gaskets to the metal ones while I have everything apart on the chance it may even be an exhaust leak on my Kooks headers contributing to the ticking noise.

Its a pain but if thats what it takes you gotta go for it.

Scott Long
08-13-2003, 12:26 AM
Ok I have now went through two 16.4 oz propane tanks w/ a torch extension on them and it made no difference. The car is still idling around 1700-1800 rpm and will ocassionally surge up higher.

I spray on the top, collar nut, upper and lower IC connections, rear IC to plenum connection, throttle body, intake manifold rear and plenum connection, sprayed down the back of the blower, all around any vac line and fitting, and still nothing.

I did however find out what the misc vac. hose went to thanks to Vernon. I plugged it in and don't hear a hissing any more. So before when I was hearing was the PCV pipe leaking.

I'm about out of ideas..... I really don't want to tear this god damn motor apart again.

I had a hell of a time sealing up the lower IC tube at the intercooler, I could only get it as tight as I could with a box end 13mm wrench. I might pull the left side accessory bracket off, and take the lower tube off, tighten it up at the IC, and put it back on the car.... but I have the top RTV'd to the blower so it will be major *** pain to get it all apart and not disturb the top since I don't own a spanner nut wrench. Anyone want to send me one to use and I'll pay you back for the shipping, and ship it back when I'm done?

Oh by the way I have the metal header gaskets and they sealed up AWESOME, no exhaust leaks except around my flex pipe till I get it to the exhaust shop for new pipes.

MIKE 38sc
08-13-2003, 12:38 AM
OK Scott it looks like you fixed part of it. The PCV is plugged back in and your idle has dropped alittle so your heading in the right direction. The vac test pass's. Next thing to check is the IAC.
Have you checked it?
Are you posative that it works or not?

Scott Long
08-13-2003, 12:50 AM
Well I let someone else use it for a few months and it worked on their car. I guess I could swap the other one off my 92 SC....

But why is it still running lean enough to get the headers red hot? The exhaust is not making any smoke and doesn't have a distinct smell. If anything I'd say it smells lean.

The only thing I can imagine might have the slightest leak would be the lower ic tube to ic connection. Thats why I want to remove it from the car but leave it attatched how it is so I can tighten it down with a ratchet and then re-install it on the car and hook the upper tube back to it. I need a spanner wrench because I don't want to take the top back off the blower since it's RTV'd on really good and I sealed up a massive leak it had there.

I don't hear any hissing anywhere.

MIKE 38sc
08-13-2003, 12:59 AM
Well when the diaphram inside tha IAC goes bad it lets alot of extra air into the intake past the throttle blade and to the engine it looks like the throttle is open so it runs at a high idle RPM.
Make sure the IAC is working and let us know.

BobGPz
08-13-2003, 01:05 AM
Mike...remember my IAC problem?? 2k rpm..excess heat...excess fuel??

I too was foolish enough to CLEAN out the IAC when chasing illusive problem. Bad call I made! It screwed it up. I unplugged it with motor still running and I thought that was suppose to kill the motor. It didnn't.

I replaced my IAC and gasket and what a miracle that ~~~ can do to a car.

MIKE 38sc
08-13-2003, 01:14 AM
Yes I remember.
I know all too well what trouble that part can cause.
I've chased that demon myself!
Thats why I'm trying to help.
Most of the time its the simplest things that cause the most problems.

Scott Long
08-13-2003, 01:23 AM
Ok well when I had the motor apart and when I painted the throttle body I took both the IAC and TPS off of it and cleaned the IAC w/ a q-tip and engine degreaser. It was black before and now the diaphragm is yellow. It makes no difference when I unplug it, so maybe I will replace it. How would that make it like a vac leak, if its coming throught past the maf in the intake hose wouldn't it still be "metered"?

MIKE 38sc
08-13-2003, 01:41 AM
Yes Scott it would be metered but things would still be out of wack because of the info the TPS is sending to the comp. The comp see's the engine idleing high but the TPS is telling the comp that the accelerator is at idle. So its kinda confused right now.

If you cleaned it with a Qtip you probably ripped the diaphram and didnt notice it. That thing gets brittle with age.

Rob Noth
08-13-2003, 03:12 PM
Scott, have you changed those O2's yet? That probably isn't causing the high idle, but it is probably the cause of the glowing manifolds.

Mike, what you said about the computer working to prevent lean conditions is right, and that's exactly why I would replace the O2 sensors here, because even with a big huge vacuum leak, the computer is usually able to correct the mixture and prevent running lean. If it can't correct it, you would get one of the adaptive limit codes (there are a bunch of them).

If you don't have a code, and the mixture is way lean, then the computer thinks it's running right, but of course it's really not, because the 02 sensors are giving inaccurate data.

BobGPz
08-13-2003, 06:26 PM
Scott...
Try a different IAC Valve. I heard you say you had an extra one, so it won't cost you anything. All I did was clean mine out with some ...ooops...brake cleaner and it to became yellow inside. Nice and clean. Clean equals good working part. Right? Wrong! Either the gunk in there was holding it together, or the cleaner ate it. Either way it won't cost you anything to try it.

As Mike said..chasing the demon...Well I chased it round trip too. I bought new O2 sensors @ $82.00...nothing. Bought new TPS @ $55.00...nothing. Tried another set of fuel injectors @ $100.00....hardly nothing. New TB, IAC, IC, and Intake GASKETS @ $40.00...nothing. Pulled all electrical wiring off engine and checked for cracks or bad sensors and retaped it up nice and neat @ 3 days work....nothing. Someone had me pull the IAC plug off when running, which should kill the car cause air can't get to the TB withought the computer to tell the IAC how open it is. I replaced the IAC and gasket and Whaa Laaa! I'm laying my new Michellin Pilots all over the road. Really had a hard time understanding why that little thing caused such a big problem, but it did. Give her a shot.

Scott Long
08-13-2003, 08:57 PM
ok, i'll get a new set of O2 sensors and get a new IAC. Might as well, at least I'll know they are new right?

BobGPz
08-13-2003, 09:08 PM
Personaly I wish I had spent the $82 on something else like a road trip with lots of pizza rather than the O2 sensors. Try the IAC first, cause mine still clogged up my new O2's cause the IAC was still bad. But I see your point that about Piece Of Mind, and not having to worry about them later. POM is expensive, isn't it?

MIKE 38sc
08-13-2003, 11:45 PM
Scott just do not install the new O2's until you get the idle problem solved, you do not want to cook the new sensors right off the bat. O2 sensors cannot make the engine idle high, if the O2 sensors go out the comp sets the mixture rich(goes to open loop oporation) for safety reasons and that will only make the engine idle rough and use more fuel.
Put the new IAC on and Ill bet you the idle drops back to normal RPM. Now it might be idling alittle rough but not bad but the RPM will drop.
After you got the car idleing again shut it down , let it cool, then put your new O2's in.
I think you will be happy.

Scott Long
08-14-2003, 05:14 PM
Could I theoretically unplug the O2's and put on a new IAC and run the car. If it idles good and doesn't heat up the manifolds then I will know for sure the O2's are shot. I would assume the O2's would set a code if they were making the engine run that lean unless somehow they are not changing voltage but staying within the rich limits. Then the computer would lean out the mixture and not constantly adjust it causing my manifolds to turn red hot? Does that sound right?

Scott Long
08-14-2003, 08:19 PM
Well I just pulled off my IAC and inspected it and the diaphragm is cracked and I was able to shake it and pieces of it came out. I guess its just too old and brittle and wore out. So my friend is gonna let me borrow his extra IAC and I unplugged my O2's for testing purposes to prove my theory. Should know within an hour or two......

MIKE 38sc
08-14-2003, 09:37 PM
Scott your engine will run without O2 sensors, But trust me there is NO way they will make your engine run that lean.
I would suggest that you buy your own new IAC, reason is you may destroy your buddies by disturbing it. You saw how brittle that diaphram was and your buddy's if it is old will be brittle also.
You could end up having to buy 2 of them if you screw your buddy's up by messin with it.

Scott you now see that I was right about your IAC. I'm NOT lying to you about the O2's. They will not make your car idle high, its impossable. If your O2's go bad the only thing that will happen is it will idle a little rich and the idle will be rough. Thats ALL.

You stated that if your car would idle with a new IAC and the o2 sensors unplugged, that would prove your O2's are bad.
Hows that?
Who's telling you this stuff?

Scott Long
08-14-2003, 10:55 PM
Ok it runs!!!!!!! And idles good now with the IAC changed. I unplugged the O2's and it doesn't get red hot. I put a new fan on it also and it keeps the temps right below the N and it also has a new temp switch.

Its throwing a CE light every now and then probably from not having the O2's plugged in. I think they are bad and if I plug them in it might run lean again, not sure though...

MIKE 38sc
08-14-2003, 11:36 PM
OK Scott! Disconect the battery to reset the comp. Hook the battery back up after waiting about 60 seconds. That will erase the codes.
Now hook up you O2 sensors and start the engine back up, just let it idle. The comp will start learning and adapting to the engine. After idleing for about 10 minutes the engine will start smoothing out and running better. If you get a CEL after resetting the comp pull the codes and see what they are. If you dont get a CEL your O2's are fine.

Its amazing how much troulbe an IAC can cause isnt it?

Rob Noth
08-15-2003, 12:06 AM
If it doesn't glow with the O2 sensors disconnected, that's a pretty good sign they were causing that problem. You can try running it again with the old sensors, and see if the manifolds are glowing, but by that time you may have already damaged the engine. Personally I wouldn't take the chance. It's a well known fact that antifreeze ruins O2 sensors.

BTW a bad IAC would not cause the car to run lean to the point of glowing manifolds, because the air coming through the IAC is metered through the MAF, and also because properly working O2 sensors will allow the computer to control the mixture, even if there had been a vacuum leak.

Scott Long
08-15-2003, 12:11 AM
Well I am now back at home, and have put about 25 miles on the SC going no more than about 5 psi trying to break it in. I did however blow part of my exhaust off, since it was just clamped on. I'm sure the neighborhood is gonna love me!

I was almost home and the CE light came on. I think the O2's are shot. I am not gonna bother trying them, I'll just buy new ones.

The IAC on the car now is much better.

Thank you guys for all your help. I'd have torn the motor back apart if it wasn't for everyone's help. I thought for sure it was sealed up good because I RTV'd and torqued down everything and made sure all my vac lines were good and connected to the right place.

Here she is, after being in the garage since December of 2001!!!
http://members.tccoa.com/slong92/sc/scott3.jpg

http://members.aol.com/kenwoodsc/images/sc2.jpg

BobGPz
08-15-2003, 01:05 AM
IAC is such a pain eh? Happy for ya Scott! Yours looks like my '90 SC. Great having people help ya when you've spent so long working on her and she won't work right eh? I guess there are at least two of us that will never clean out a IAC again.

I can't see how it is possible to glow the manifolds when O2's are bad. If anything they would just run rich. Did you pull the batery cable to reset (erase) the stored codes? If so, now pull the codes and see what the CEL is saying.
:D :D :D

MIKE 38sc
08-15-2003, 01:11 AM
Listen to Bob Scott, pull the codes now and see what it says.
Post the code and we will rap it up.:)

MIKE 38sc
08-15-2003, 01:16 AM
Originally posted by Rob Noth
If it doesn't glow with the O2 sensors disconnected, that's a pretty good sign they were causing that problem. You can try running it again with the old sensors, and see if the manifolds are glowing, but by that time you may have already damaged the engine. Personally I wouldn't take the chance. It's a well known fact that antifreeze ruins O2 sensors.

BTW a bad IAC would not cause the car to run lean to the point of glowing manifolds, because the air coming through the IAC is metered through the MAF, and also because properly working O2 sensors will allow the computer to control the mixture, even if there had been a vacuum leak.
Rob could you please explain to me how that works?
What are you basing your explanation on of how the ECU system works?
I dont find any data that supports what you are saying.
Could you please direct me to it? I'd like to take a look at it.:confused:

Rob Noth
08-15-2003, 01:42 PM
OK Mike, you asked for it, here is the long explanation... :eek:

A good reference is "Ford Fuel Injection & Electronic Engine Control" by Probst, it has the best explanations. Bosch also has some engine handbooks that are good. But it's really quite simple.

The ECU operates in a closed loop mode during normal driving conditions. This means it continuously adjusts the mixture based on the signal from the O2 sensors. If you have a vacuum leak, or low fuel pressure, or other problems that could affect the mixture, the O2 sensors will show that the mixture is off, and the ECU will compensate by increasing or reducing fuel injector pulsewidth. This adjustment is known as the "Short Term Fuel Trim" (you can read it with a scan tool on DCL-compatible cars '92 and up).

So if the car is running lean and the manifolds are glowing, there can only be a few reasons for this.

1. the computer itself is broken or programmed wrong with an EEC tuner.

2. the problem is so severe that it's outside the +-25% range of the adaptive control. But in that case the car wouldn't be running well, if at all. And Scott said it was running OK except for these problems.

3. the O2 sensors are giving inaccurate data. If the O2 sensors keep saying the car is running rich, even when it's not, the computer will keep making it leaner.

In case you really want to know, the reason antifreeze ruins O2 sensors is that antifreeze contains small amounts of silicates as corrosion inhibitors, and when this gets in the exhaust stream like through blown headgaskets, it contaminates the zirconium dioxide ceramic element in the O2 sensor. This element has one side exposed to the exhaust gas, and the other side exposed to air. When heated, it generates a voltage based on the difference in oxygen content between the two sides. When contaminated, the O2 sensor may see less oxygen in the exhaust stream than is really there. And of course less oxygen in the exhaust means rich, so the computer keeps trying to make it more lean.

MIKE 38sc
08-15-2003, 02:28 PM
Well Rob I happen to have that manual as well as many others so I'm glad that were on the same wavelenght here.
I fully understand how the ECU system works so thats not going to be a comunication problem for us.

#2 in your list of problems was the entire reason that Scotts manifolds were glowing, like I've been saying all along.
When he had such a catastrophic failure of the IAC diaphram that put his parameters well outside the + or - range of 25%.
Thats why when he replaced the IAC the idle dropped back down and the manifolds quite glowing.

I'm well aware of the toxisity of antifreeze on O2 sensors, but it would take several more sensors in the system to go out along with bad O2's to cause the manifolds to glow like that

You stated that if Scott unplugs his O2's and his manifolds werent glowing that that was proof they were bad. Yet you made no mention that he had just fixed a GIANT vac leak by replacing the IAC. He had done nothing else to the engine at that time except replace the IAC and he said the manifolds werent glowing, so how did you come to the conclusion that the O2's were responsable for the engines progress?
I mean they were unplugged, rendered useless before and after he changed the IAC. Only after he changed the IAC did the engine start to work more properly.
Thats what has me confused. I just dont understand how you think the O2's had anything to do with the engines progress since they were disabled before and after the improvement.

#3 in your list is accurate however there would have to be failure of the TPS as well as the BAP and the ECT at the same time in order for that scenario to even have a chance to happen.
Scott didnt have any codes for any of that, at least he didnt mention any.
So what evidence did you use to come to the conclusion that that was what was happening, other than the glowing manifolds?
Scott already said that since he changed the IAC the manifolds quite glowing, so I'm having trouble understanding why you think the O2's had anything to do with it since there the same O2's and there still disconnected.
If the O2's were telling the comp that the engine was rich the comp would compaire readings from the TPS the BAP and the ECT sensors and could tell if the O2's were oporating outside there normal parimeters and if they were it would then go to open loop oporation in order to protect the engine. Problem was he had that nasty vac leak and the system could not compensate for it.

I'm just trying to understand your line of thinking on this thats all.
I'm not trying to be an ***.:)

Rob Noth
08-15-2003, 04:06 PM
No hard feelings of course, I enjoy a good debate. I think the point where we don't agree is the broken IAC sensor. I'm saying it's not a vacuum leak. The ruptured diaphram will not introduce any unmetered air, unless the whole sensor case was cracked open to the outside. It just allows more air to bypass the throttle plate. It's exactly like having the throttle open a little bit extra. This will cause a high idle, just like if the throttle plate wasn't closing. But it won't affect the mixture.

My whole point in #3 is that if the O2 sensors are inaccurate, but not shorted or otherwise outside operating parameters, the ECU may not know they are wrong. It doesn't check O2 sensor readings for accuracy against TP, ECT, BAP, or other sensor values, or at least so says everything I've read. It only evaluates whether the signal is within the valid range (i.e. not shorted or open), and how quickly it switches. Although for that the threshold must be pretty low, because I've had some really slow O2 sensors never set a code.

The adaptive strategy uses the O2 sensors to correct for inaccuracy in the rest of the system. So if your TP, ECT, BAP was wrong, it would compensate for that based on O2 sensor feedback. But it doesn't work the other way around, an OBD-I system can't correct for inaccurate O2 sensors.

If you don't believe me, take Scott's old sensors and put them in your SC. But I wouldn't recommend that because you'll have some glowing manifolds!

BobGPz
08-15-2003, 04:42 PM
The ruptured diaphram will not introduce any unmetered air, unless the whole sensor case was cracked open to the outside. It just allows more air to bypass the throttle plate.

I don't mean to butt in, but I just can't understand this. A MAFS measures what? The TEMPERATURE of air or the VOLUME of air coming in?

If it measures the Temp than I see Mike's point, it would measure the temp of air and take that with the BAP sensor to a pre-designated formula of how much air SHOULD be coming in.

If it measures the AMOUNT than I see Rob's point that the air has been METERED by the MAFS. But I don't think the MAFS does this.

I am obviously guessing here, but SHOULDN'T the MAFS be sort of like a speedometer on an airplane telling you how fast through the wind you are travelling? If so, it would NEVER let the IAC cause problems I or Scott had. But if it just measures the temp of the air with PREDESIGNATED FACTORS burned into the EEC's EPROM to tell it that the OPENING (Inner diameter)of the MAFS is "X" amount TIMES the BAP "X factor" EQUALS "X" AMOUNT OF CUBIC AIR moving through the TB, or something like that. I should have paid more attention in Algebra class. Hey guys, I'm old school or motorcycle school here.:confused:

Rob Noth
08-15-2003, 05:04 PM
Bob, the MAF actually measures the MASS of air coming in. This is more useful than volume because it is independant of the air density or barometric pressure. (BTW I never did understand why our car needs a BAP sensor, the MAF will always read the correct air mass regardless of barometric pressure.)

What you described is more like how a speed/density system works, but luckily we don't have that!

MIKE 38sc
08-15-2003, 05:08 PM
No hard feelings either Rob. I'm just saying that you are misunderstanding what you've read, thats all.
Let me explain where youre getting of track.

First and foremost the ruptured diaphram is letting to much air into the engine in relation to the TPS reading which was telling the comp the engine was at idle. I understand that that air is metered but that does not matter because the TPS was telling the comp that the car was idleing so it was using all the fuel mixture tables for that TPS setting trying to correct the mixture problem. Since it was out of the correction factor of 25% it could not compensate for the extra air and the engine ran lean as a result.
The engine was getting too much air for the amount of fuel that was available, it does'nt matter if it was metered or not.

Do you understand what I'm trying to say or did I lose you?

Rob O2 sensors go out or get lazy with age they are considered a high wear item in the ECU managment system. Safegaurds are built into the comp itself to ignore O2 readings if they get to far out of spec and the comp will go to open loop so the engine is not damaged, if the comp itself will not go to open loop in that instace then the comp itself is bad and will set a code telling you so. Ford didnt set the allowances so far off as to ever let the engine melt down just because the O2 sensors went bad. That would be a waranty nightmare.

Youre description of how the comp sets the oporation parimeters of the engine is just incorect if the comp does not compaire any info from the TPS,O2,BAP,MAF and ECT sensors then how does it set fuel mixtures? or timing tables? That is a flaw in your thinking.
Readings from ALL these sensors ARE compaired in order to set the oporating parameters of the engine. Because of the adaptive strategy of the comp it will adjust the perimeters to compensate for small problems within the sensors and the system itself up to a point, but it was never set up to compensate for a 5/8" hole letting air into the system. Thats more than just a little problem.

As far as me putting scotts old sensors in my car, that would'nt bother me one bit. Hell I drove it for 3 months with the O2 wires cut in two, the drivers side O2 was not even hooked up and my manifold never glowed, nor have they ever glowed on any car I ever worked on or owned myself just because they were bad.
Sorry but rough idle and extra fuel consumption is all that will happen with bad O2 sensors, now you throw that 5/8" hole leaking extra air into the engine and you will end up with a lean condition. Metered air or not because the comp is using the wrong fuel tables because its getting a reading from the TPS telling it that the car is idleing so its using idle fuel tables. You said it yourself that broken IAC was acting just like you were holding the throttle open and I agree but the TPS was telling the comp that it was'nt and thats why the comp was using fuel tables that were too lean.
Idle fuel tables cannot compensate for a 5/8" hole letting air into the engine.
Do you see what I'm saying?

I think the most telling thing of all is the fact that the manifolds were glowing when it had the bad IAC, then Scott finaly changed the IAC ONLY, the idle dropped and the manifolds quite glowing.
If the O2's were causing the lean coondition and glowing manifolds, How come those problems dissappeared when he changed the IAC?
He hadnt done anything to the O2's yet, they were the same ones.

I garantee you Scott can hook those sensors back up now and the manifolds will not glow. Its just not possable unless the comp itself is screwed.

MIKE 38sc
08-15-2003, 05:19 PM
Originally posted by Rob Noth
Bob, the MAF actually measures the MASS of air coming in. This is more useful than volume because it is independant of the air density or barometric pressure. (BTW I never did understand why our car needs a BAP sensor, the MAF will always read the correct air mass regardless of barometric pressure.)

What you described is more like how a speed/density system works, but luckily we don't have that!
Rob you need that sensor because we run boost on the SC engine, thats why the NA 3.8 uses a MAP sensor.
The BAP tells the comp what barometric pressure is at that moment it then takes the MAF reading to see how much air is entering the system and from that it can calculate how much boost is present or not, it then takes that info along with TPS setting ECT temp and looks up and applies the appropriate fuel and ignition timing tables and applies them. Actually BAP sensors are used in speed density systems. The only real difference is the Mass air flow. Speed density uses a vane metering device instead of a Mass Airflow meter. Page 324 in your manual will show you one Rob.

BobGPz
08-15-2003, 05:59 PM
OK, I have to know how the MAFS measures AIR. I am a logical person and I can't see how it "WORKS".

MASS of air is measured how?
The moisture content of air is measured through a Barametric Sensor, right? Mass of my ex's butt is merasured with a 30' tape measure.:D Just kiddding.
So how is the MASS of AIR measured other than in measurement like a ruler or tape measure?
I know about the two tiny wires wrapped around and then coated, but how does that measure air MASS? Does it measure it from WEIGHT of a predesignated amount of air? I guess that would fall back to the BAP sensor with the weight of the moisture content.
Through measurement of the inner diameter of the MAFS and the speed at which it enters is the only way I can seem to comprehend this logicaly.

Yo Scott! Since this is your post, how's she running? Plug those exhaust leaks, and your O2 sensors in, pull codes cause it's almost Saturday night!!!

Rob Noth
08-15-2003, 06:37 PM
Mike, I think we might have to agree to disagree ;) My point about the sensors is not that the ECU ignores them, but just that it can't adjust or compensate the O2 sensor reading based on other sensors when it doesn't even know the O2 sensors are bad, which can happen when they are just inaccurate but not out of valid range. Disconnecting the O2 sensors is a totally different thing, in that case the ECU knows and will rely on other sensors.

BTW I had a broken IAC some years ago. It had no effect on engine operation except the idle problem. I didn't have any glowing manifolds or running lean.

Bob, the MAF has two wires inside, one heated, one not. It measures the current required to heat the wire to 200 degrees hotter than the unheated wire. Since the cooling effect of air on the wire is directly proportional to the mass of the air, it can calculate the mass by knowing how much current is flowing through the hot wire. Pretty nifty stuff.

MIKE 38sc
08-15-2003, 06:55 PM
Originally posted by BobGPz
OK, I have to know how the MAFS measures AIR. I am a logical person and I can't see how it "WORKS".

MASS of air is measured how?
The moisture content of air is measured through a Barametric Sensor, right? Mass of my ex's butt is merasured with a 30' tape measure.:D Just kiddding.
So how is the MASS of AIR measured other than in measurement like a ruler or tape measure?
I know about the two tiny wires wrapped around and then coated, but how does that measure air MASS? Does it measure it from WEIGHT of a predesignated amount of air? I guess that would fall back to the BAP sensor with the weight of the moisture content.
Through measurement of the inner diameter of the MAFS and the speed at which it enters is the only way I can seem to comprehend this logicaly.

Yo Scott! Since this is your post, how's she running? Plug those exhaust leaks, and your O2 sensors in, pull codes cause it's almost Saturday night!!!

OK Bob I dont think my own words would do it justice so let me qoute the book.

Barometric pressure:
Changing atmospheric pressure changes the density of the air. Denser air can slightly alter the air-fuel ratio and may affect how your engine operates. Some Ford engine control systems have features that allow the system to compensate for variations in air density.

Barometric pressure is the result of air pressing down and in all directions. Typical "standard day" pressures are 14.7 psi or 29.92 in.Hg.

Barometric pressure is hard to understand because we dont feel it. We live in this ocean of air with atmosphere pressing on all sides of us. But its inside too, so it balances out and we dont feel it. But our engines do. When the engine pumps air in the intake strokes, it reduces the absolute pressure below atmospheric and creates what we call"vacuum" The engine control system must feel the barometric pressure and the manifold absolute pressure and adjust accordingly.

Now I will attempt to explain how a MAF works.

The MAF has a sampling port that directs airflow across an electricaly heated wire that is in the airflow pathway thus cooling this element.
How fast the air is flowing across this element will affect how much it cools it. The signal is sent to the comp giving it a reading. The comp then looks this info up in the listed airflow tables that ford provided at the factory. Ford is the ones that tested the MAF and knows what reading means how much air is coming in.
The comp then takes that info along with TPS,BAP,IATand engine RPM and determines what fuel and ignition table to use.
After the engine enters closed loop it then takes a reading from the O2 sensors and fine tunes the air fuel mixtures, if anything ever gets outa whack the comp imediatly reverts back to open loop ignoring the O2 readings to keep from having a dangerous lean setting. That is why O2's reading wrong telling the comp to lean out the mixture will not cause glowing manifolds. Once the comp sees that the info its getting is not reliable because it doesnt jive with what the rest of the sensors are saying it will decide theres a problem and go straight to open loop and safe richer fuel tables.

MIKE 38sc
08-15-2003, 07:14 PM
Originally posted by Rob Noth
Mike, I think we might have to agree to disagree ;) My point about the sensors is not that the ECU ignores them, but just that it can't adjust or compensate the O2 sensor reading based on other sensors when it doesn't even know the O2 sensors are bad, which can happen when they are just inaccurate but not out of valid range. Disconnecting the O2 sensors is a totally different thing, in that case the ECU knows and will rely on other sensors.

BTW I had a broken IAC some years ago. It had no effect on engine operation except the idle problem. I didn't have any glowing manifolds or running lean.

Bob, the MAF has two wires inside, one heated, one not. It measures the current required to heat the wire to 200 degrees hotter than the unheated wire. Since the cooling effect of air on the wire is directly proportional to the mass of the air, it can calculate the mass by knowing how much current is flowing through the hot wire. Pretty nifty stuff.

Rob I completely agree with the way you just put it. The comp could not compensate for the IAC leak even if the O2's were brand new and thats where I disagree with you. Maybe I'm gettin you wrong but to me youre saying that if the O2's were new the comp could could set the fuel mixture correct even though the IAC was letting all that extra air in.
The only real problem with that is the comp would have to access fuel tables its programed to ignore at idle posistion via TPS. If we were to remove the TPS from the throttle body and manualy manipulate it ourselfs we could then cause the comp to access the file needed to correct the mixture, but that wouldnt solve the high idle RPM. However we could have stopped the manifolds from glowing if we hit the right setting on the TPS and corrected the fuel mixture before it melted the engine.

We could have Scott prove or disprove my theory very easily if he would like to.
He can install the new O2's and then simply put that bad IAC back on. I'll bet you a steak dinner if he does that those manifolds will glow again.

My SVT has 4 O2's and its manifolds wont glow if they go out. But if the IAC goes like Scotts did they will.

Rob the amount of damage to your IAC could not have been as bad as Scotts and that would explain why his was so much worse.
The diaphram doesnt always tear the same amount on every failure, some are worse than others.
The way Scott descride all of the diaphram parts falling out of it it deffinetly sounded like a catostrophic failure and that is pretty rare. but as we have seen it does happen.

Scott Long
08-15-2003, 08:29 PM
Well she's running pretty good. I just gave it a 10 psi run through first and put it up into D and she gave me a good chirp hitting 2nd gear. It doesn't feel as fast as my 5-speed SC but the speedometer moves up there pretty quickly.

As for the debate. Good reading, I've learned a lot. I think the part about the IAC letting in too much air w/ the TPS showing an idle setting is true. I am going to replace my O2's since I'm sure they are old and shot. If anyone would like these to test with I'd be happy to send them to you in a few weeks once I get around to finishing this car all up. It runs and I'm happy so for now I am gonna start saving up for my exhaust system and O2's, gears, lowering springs, and blower pulley. I have been off work now for over a month due to being hurt. Thats why I finally after almost 2 years finished rebuilding my engine. I have been getting screwed by workers comp. and not being paid nearly enough of what I usually make and they were supposed to continue my full wages. Well I go back sunday and then after 2 weeks I'll get money to buy more goodies for this car. I want to run one of my cars at the SC shootout in Sept. I don't know if this car will be done to where I want it by then or not though.

Once again a big THANKS to all who have helped me. I was so close to tearing it back down to the heads and resealing EVERYTHING. I am glad I didn't have to do that.

Thanks to Steve Scudder (Biker SC) for the IAC valve. I'll get a pic of me doing a big smokey and post it for you guys.

BobGPz
08-15-2003, 10:00 PM
How fast the air is flowing across this element will affect how much it cools it.

Not to wear your knowlege out here, but wouldn't WARMER air NOT COOL the 2 wires down as quick as COLD air would, thus changing everything since alot more warmer air would be needed to cool than cold air? Or am I thinking to deeply here?

Glad to hear she's a runner Scott.

Big Cat Davo
08-15-2003, 11:35 PM
You got it exactly right Bob. Warm air will have less mass than an equal volume of cold air, it will cool the wire less and as a result the engine will know that less air in entering the system.

Dave

MIKE 38sc
08-16-2003, 01:29 AM
Scott I'm just glad your car is doing better! and that you didnt have to tear it back down. That was my whole goal. Glad it worked out for you.
Rob and I may have disagreed on what was going on with your car but sometime during the debate your car got fixed, so something good come from it all.
Rob I enjoyed the talk and hope we talk again in the future.
Everyone should buy the book that Rob mentioned titled:

How to Understand, Service and Modify Ford Fuel Injection & Electronic Engine Control. By Charles O. Probst, SAE

Robert Bentley is the publisher.
You can buy the book at any Ford dealership parts dept, Amazon.com, Barnes & Noble, Books A Million, Summit Racing just to name a few.
The book has the FULL endorsement of the Ford Motor Co.
I beleive the last Ford Motorsport catalogue I looked at refered to the book as the bible on the Ford EEC-IV, so it is a valid piece of technical information.
If you get this book, read it and understand it you will be able to easily trouble shoot and fix ANY Ford system using the EEC-IV not just the SC so that comes in handy for those of us with more Fords than a SC.
The book sells for $30.00, replace 1 uneeded MAF sensor because you thought you needed one and you could have bought 2 books. Get the book! :) and stop buying uneeded parts.
The cars alot cheaper to own that way.

MIKE 38sc
08-16-2003, 01:35 AM
Originally posted by BobGPz
How fast the air is flowing across this element will affect how much it cools it.

Not to wear your knowlege out here, but wouldn't WARMER air NOT COOL the 2 wires down as quick as COLD air would, thus changing everything since alot more warmer air would be needed to cool than cold air? Or am I thinking to deeply here?

Glad to hear she's a runner Scott.
Bob youre catching on.;) That little comp is doing an awfull lot of things that most people dont realize. I'm glad to help anybody, but if I give you a fish I've fed you for a day, on the other hand if I teach you to fish I've fed you for life.;) If you know what I mean!
Go buy that book with some of that money I saved you(LOL) and start fishing!;)

BobGPz
08-16-2003, 09:48 AM
That is my intention, to learn this stuff so I can do it myself. Then the local Ford dealer won't be ripping the shifter out of my transmission again and blaming it on a "13 year old plastic clip" while "Test Driving" my ride. Had 3 different places trash my ride while "Test Driving" it. Gettting sick of it. I'd rather they test drove my ex than my car. Thanks again for info!!

Scott Long
08-16-2003, 01:07 PM
I will not take my car to a shop unless its something I am not capable of fixing (which isn't much) or something I don't have the equipment/tools for (isn't much either). I would have rather torn that motor back down, resealed everything, and be out only my time, than to have the shop tear it down and do the same thing and charge me $70/hr. to do it. I think I sank about $600-800 into it and I have a sweet running car. Had the shop done it I would be over $2000.00 w/ parts and labor and I would have probably sold the damn thing as a "mechanic's special". Luckily for me I have been working on cars since I was young, took shop class in high school, and I'm in my early 20's and I have a job managing and auto parts store. I also can afford to own two awesome SC's and repair them myself. I hope to keep these two cars forever.

MIKE 38sc
08-16-2003, 01:34 PM
Scott you can probably get that book Rob mentioned at your place of work. I have seen them at some parts stores.

Scott Long
08-16-2003, 01:53 PM
I'll check tomorrow when I'm at work and see.

BobGPz
08-17-2003, 02:05 PM
Glad to hear she runs great Scott!

The self satisfaction every time you drive her is that you did it yourself and that is more valuable than any amount of money you may have saved.

And the knowledge we have not to EVER clean out the IAC again! Hahaha

Scott Long
08-17-2003, 09:18 PM
I have gotten a lot of compliments on the car. One guy couldn't believe it was a 1990 model and when I let him read the odometer he was in shock.

I can't wait to start the bolt ons on this car!!! First will be exhaust, pulley, gears, intake, and ud pullies. Those are the best bang for the buck mods and it will feel like a different car. The 5-speed responded well to those mods.

MIKE 38sc
08-17-2003, 09:31 PM
Scott did you ever put new O2's on or are you still using the old ones?

Scott Long
08-17-2003, 11:08 PM
still unplugged and runs fine, but damn I use a lot of fuel. I'll be getting a new set when pay day rolls around.

MIKE 38sc
08-17-2003, 11:11 PM
Plug em in and try them. Nothings gonna glow;) If I'm wrong you can just unplug em, but if I'm right you'll buy less gas!
Give it a try, you got nothing to lose.

Scott Long
08-17-2003, 11:30 PM
I'll give it a try tuesday, thats the first day I'll have time to climb under it. Its dark out now, and I work all day tomorrow.