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choltz
11-20-2008, 12:14 AM
Hi,

89 5spd, 185K miles

I've been reading and searching the forums for some ideas on this problem, but so far no luck. A couple of weeks ago I noticed that the engine was never idling down below around 900 RPM. I've seen high idles before when the IAC bellows was broken, so I took off the IAC and it didn't look bad, but I replaced it anyway. No difference on the idle. Since then, the engine has started revving up, sometimes as high as 2500 RPM and just sitting there. I'm pretty sure the computer is doing it since I can unplug the IAC and the RPMS drop back to normal. The CEL is on all the time, but the only code I get is a SPOUT signal failure (49). I'm pretty sure this is DIS related, but I've had problems with that for a long time and I don't think it's related to the revving problem.

I'm at a loss here since I'm not getting any codes that seem related. I've been trying to think of why the computer would command the IAC to rev the engine so high. I thought maybe I've got a fuel leak somewhere causing a rich condition and the computer trying to counteract it, but my fuel mileage hasn't really changed much. Also, I would expect the computer to throw a code for a rich condition. Also, it even revs up immediately on startup after it's been sitting a work all day. In that case I wouldn't expect the computer to be even looking at the O2 sensors since they're cold.

I have 20in vacuum at idle (900 RPM), so I'm not thinking a vacuum leak. I've also put a VM on the TPS and it seems to be OK (around .8 volts closed up to around 4.5-5, nice and smooth).

One final symptom, the engine fails to start once it's warmed up. Acts like it's flooded. I have to hold the pedal at WOT and get partial starts 5-10 times before it will finally run again. To me that points to a fuel leak somewhere as well.

Other than the high idle and revving (which is getting more frequent everyday) the engine runs pretty nice. No problems starting after the engine cools down.

So, any help? I've had the car since about 79K miles and rebuilt the engine once. This is a new one for me!

Thanks in advance!
Corbin

james5275
11-20-2008, 12:41 AM
Did you replace the IAC with a new one from Ford? Aftermarket ones won't work (I'm sure anyone else here can explain why). Does the engine make a strange noise? A hooting sound is a good sign the a the IAC has failed.
At this point, I would think the IAC is also causing your hard starting. Just a hunch. Start with the simple stuff. Have you made any other changes in the engine management lately?
jj

mywhite89
11-20-2008, 09:09 AM
I am having this same problem with my car to the tee. I gave up and put mine away for the winter. I have replaced the IAC which did not fix the problem and changed out tps sensors although mine checked out just fine. I am getting the spout code as well, also pulled a tps code which I think was related to the high idle problem, not necessarily a tps sensor problem. Check out my thread: http://www.sccoa.com/forums/showthread.php?t=103417

Notice where I have flucuations of voltage when I use the battery as my ground source versus using the blk/white wire on my sensors? The black/wht wire is the ground source for the sensors. You might want to check that on your car just for point of reference. The same ground source is used for several sensors inlcuding the tps, bap, and various others. My problem is very intermittent, so maybe you'll be able to track yours down easier if yours does it all the time.

Check a spark plug and see if the problem is causing your car to run rich also.

I'll fax you wiring schematics if you are willing and capable to check these things. Anything I can help you with just ask, 260-341-2216.

Chris

P.S. the no start when hot condition sounds like a different issue. I don't have that problem ever. Oh and the part number for the iac sensor is stamped on it, so you would know if you've got the wrong one.

choltz
11-20-2008, 09:20 AM
Thanks for the reply!

I used an aftermarket IAC, but the one that was on there already (and has been for more than 10 years) was an aftermarket part also. And as I stated, I can unplug the IAC and the engine idles back down to almost normal which I assume means that the EEC is actually commanding the IAC to the fast RPMS (in other words the IAC isn't leaking that much). I would agree that the IAC could be causing the engine to never idle below 900, but I don't think that is causing the 2500 RPM idle. The hard starting only occurs when the engine is warm, and I get a lot of black smoke when trying to start it. Again, part of the reason I was thinking flooding of some sort.

Something occurred to me the morning. Is it possible that the DIS problem is related such that the EEC isn't getting a tach signal and therefore doesn't actually know the RPMS? When I've done the KOER test most recently, I got a 11 (OK) code from the on demand, but I'm always getting a 49 (SPOUT) in the memory codes. My tachometer does work, but I'm wondering if the tach uses a separate signal than the computer does? I know the engine won't run if the DIS doesn't get the crank/cam sensor signals (up shift light, been there), but can the DIS keep the car running if the EEC doesn't get a tach signal? Isn't that what disconnecting the SPOUT plug near the DIS does when you are checking initial timing?

Just more things to think about!

Thanks!

mywhite89
11-20-2008, 09:28 AM
By pulling the spout plug you disrupt a ground to the computer, magically black/wht wire again. Actual function of how this all works is still a mystery to me.

choltz
11-21-2008, 09:22 AM
I wanted to post a correct to my original email. I stated that the Check Engine Light was on all the time, but that was wrong. The Check Gage light is the one that's on all the time. My speedo has been messed up for months, so I assume that the cluster somehow knows there's something wrong. All of the other gauges seem to be OK (other that the gas gauge which is just a pain).

I played around a little last night, reran KOEO/KOER tests. Still no on demand codes even though the engine seemed to doing it's extremely high idle thing during the KOER test. After clearing the memory codes, I cranked it back up and started unpluging things just to make sure the engine would throw codes. Got everything I expected: MAF, BAP, ECT, ACT, TPS, IAC. I didn't try the O2 sensors (didn't have the car up).

A little clarification on the hard start problem. It seems to happen only when the engine is warm, but only after it has sat for a while. If I shut the engine off, it will start fine within a couple of minutes (maybe < 5?). But if it sits longer than that, you're pretty much not going to get it to start until she's almost dead cold again. It sat for 45min at work here yesterday morning and when I tried to go somewhere I couldn't get it to start. Again, if I hold the gas pedal all the way down (flood clear), it will hit, but won't stay running. And you can do that over and over again.

If I had a single injector slowing draining the fuel rail, I wouldn't expect it to keep the engine from starting, just make it upset when it did. I did see a post where someone was talking about the fuel pressure regulator going bad (broken diaphram) and fuel going back up the vacuum line, but I wouldn't think there would be enough fuel in rails to flood the entire engine.

The engine tend to get a little warm when it's idling at 2500 RPM and I starting to think about just unplugging the IAC until I get it figured out, but I'm worried I'll have decel problems with the 5spd.

Any ideas would be greatly appreciated! :D

Thanks,
Corbin

TbirdSCFan
11-21-2008, 03:28 PM
I wanted to post a correct to my original email. I stated that the Check Engine Light was on all the time, but that was wrong. The Check Gage light is the one that's on all the time. My speedo has been messed up for months, so I assume that the cluster somehow knows there's something wrong. All of the other gauges seem to be OK (other that the gas gauge which is just a pain).

I played around a little last night, reran KOEO/KOER tests. Still no on demand codes even though the engine seemed to doing it's extremely high idle thing during the KOER test. After clearing the memory codes, I cranked it back up and started unpluging things just to make sure the engine would throw codes. Got everything I expected: MAF, BAP, ECT, ACT, TPS, IAC. I didn't try the O2 sensors (didn't have the car up).

A little clarification on the hard start problem. It seems to happen only when the engine is warm, but only after it has sat for a while. If I shut the engine off, it will start fine within a couple of minutes (maybe < 5?). But if it sits longer than that, you're pretty much not going to get it to start until she's almost dead cold again. It sat for 45min at work here yesterday morning and when I tried to go somewhere I couldn't get it to start. Again, if I hold the gas pedal all the way down (flood clear), it will hit, but won't stay running. And you can do that over and over again.

If I had a single injector slowing draining the fuel rail, I wouldn't expect it to keep the engine from starting, just make it upset when it did. I did see a post where someone was talking about the fuel pressure regulator going bad (broken diaphram) and fuel going back up the vacuum line, but I wouldn't think there would be enough fuel in rails to flood the entire engine.

The engine tend to get a little warm when it's idling at 2500 RPM and I starting to think about just unplugging the IAC until I get it figured out, but I'm worried I'll have decel problems with the 5spd.

Any ideas would be greatly appreciated! :D

Thanks,
Corbin

Do the IACs that you tried have a white colored "bellows" like cover inside the end that sits closest to the connector?
When you traded out the IAC, did you install a new or used one?
The replacement that you tried, did it have a cable lead?

The fact that the car idles w/o the IAC makes me wonder if you did something to the throttle plate setting. Throttle plate should be completely closed, but not binding, at the rest position with the cables attached. No gap!

Lastly, have you done anything at/around any of the intake, especially the IC tubes, recently?

KMT
11-21-2008, 04:30 PM
Replace the IAC....again.

kevsha
11-21-2008, 04:54 PM
With the IAC connector off the car should stall because it should close fully. so it seems to me like you may have a vacuum leak, the iac haas failed and will not close fully or throttle plate will not close fully.

KMT
11-21-2008, 05:16 PM
>With the IAC connector off the car should stall

Almost stall - the engine might stumble and then hunt for/settle at a slightly low idle...not stall outright.

choltz
11-22-2008, 12:12 AM
The IAC is the correct one. Everyone keeps saying that I should replace the IAC again, but I don't understand. The EEC knows the RPM of the engine and controls the RPM using the IAC. It's a closed-loop system, right? If the engine is turning too fast, the computer will control the IAC to lower the RPM. I know the computer can control the IAC because it does so during the KOER test and will throw a code if the computer does not see the expected RPM drop. In the case of my problem, the computer is commanding the high RPM for some reason. I'm just trying to figure out why?

What would cause the EEC to raise the RPM above an idle? My A/C is disconnect, so it's not that. It would obviously raise the RPM to try to keep the engine running if the idle drops too low. But why 2500 RPM?

Thanks for all the responses!

KMT
11-22-2008, 12:49 AM
>The IAC is the correct one. Everyone keeps saying that I should replace the IAC again, but I don't understand.

Seen this msg.? (http://www.sccoa.com/forums/showthread.php?t=66448)

Can you upload photos of the new IAC on & off the car?

>I'm at a loss here since I'm not getting any codes that seem related.

>...and will throw a code if the computer does not see the expected RPM drop

What codes have you seen...can you list them all...?

>My A/C is disconnect, so it's not that.

Anything else disconnected?

choltz
11-22-2008, 09:43 AM
OK, according to the message you pointed me to, the wrong IAC won't even fit, so how does somebody put the wrong one in? I replaced the original Ford unit with a matching aftermarket one. The one I just put on there was identical as well.

And, I'll say again that the IAC works just fine during the KOER test. It raises the idle as necessary (including when you do the cylinder balance test which I did and everything passed), and it cuts the idle down to around 700 during the part of the test where it tries to lower the idle. I've been through this already in this thread. I'm certain a bad IAC is not causing the 2500 RPM idle, the computer is commanding the 2500 RPM.

I'm very glad for all the help, but does anybody have any ideas other than the IAC?

Thanks,
Corbin

fturner
11-22-2008, 09:54 AM
Start with the with the basics first before you start thowing money at everything.

1. Disconnect the battery for 15 minutes or so.

2. While waiting, take your maf sensor out and clean it up. Use a dab of isopropyl alcohol on a cotton swab and gently clean the elements.

3. Make sure there is nothing binding up around the throttle cable(s), and that the throttle has full range of movement. The car should be able to idle without the IAC plugged in albeit lower than normal. The throttle plate should actually NOT be fully closed but should have enough of a gap to see light, but you'll have to take the throttle body off to see that. The computer actually has a parameter in it that specifies the amount of air that is getting past the throttle plate.

4. Check for ANY vacuum leaks....

Have you added anything to the car mod wise that you haven't told us here?

Frit

choltz
11-22-2008, 10:15 AM
Sorry, I got interrupted and forgot to answer the other questions.

I cleared the codes the other night and drove to work yesterday, and it did do it's screaming-idle thing. Checked the codes and got nothing (11=OK) for both on demand and memory codes.

The A/C unplugged because the front seal on the compressor is shot and I haven't been able to figure out a way to get the stupid snap ring off the front without the special tool. Nothing else is unplugged.

choltz
11-22-2008, 10:28 AM
Thanks for the reply, Fritz.

I unplugged the computer the other night.

I haven't cleaned the MAF sensor, I'll do that today.

I've check the throttle linkage, everything looks good. I check the TPS sensor the other night as well. Voltage was around .8-.9 closed and 4.5-5 open, nice and smooth with no dead spots or spikes.

I've tried to check for vacuum leaks. I've always heard you could use propane but have never had any luck. Just know I went out and tried again. I neither heard the RPMS increase. I even unplugged a vacuum line, which didn't seem to affect the idle at all (currently idling around 950 RPM). Then I shot propane down the leak I created and still didn't get an RPM increase. Maybe I'm expecting too much RPM increase?

There are no mods on car. She's bone stock. I've never really had extra money to spend on it, other than to keep it running. I've owned the car since about '93 (79K) and she now has 189K miles. I've rebuilt the engine once, trying to solve a problem, before I knew better. That time, it just needed new plugs & wires. I've certainly learned since then!

Thanks again!

mywhite89
11-23-2008, 03:20 PM
I still find it interesting how how you are throwing the same code I am, spout code and having the same problem. Something in that field has to be the problem. I have 2 extra IAC's on top of the one I already have replaced. I could keep putting different ones on, but the fact is that did not fix my problem or even change anything.

Oh I was thinking about your hard start problem. Test your coolant temp sensor, the one next to the DIS module. If it constantly tells the computer that your coolant is cold, that changes the paramters for starting the car and could explain the reason why warm starts are an issue. http://fordfuelinjection.com/index.php?p=28 Just a thought and something to check out. Otherwise I've heard on here where something is overheating in the DIS and you have to wait till its cooled down to start. Would help if you were able to switch it out when you have the occurance of course. That would tell you right away if that was the issue, but I know those things are expensive to buy new.

KMT
11-23-2008, 03:48 PM
>according to the message you pointed me to, the wrong IAC won't even fit, so how does somebody put the wrong one in?

Easy. Read it again....

The ports in the wrong IACs are opposite what they should be for use on our engines. One of those will fit if you ignore the ports. People unknowingly bolt it on in what they think is the correct orientation, but that won't allow it to operate correctly. They can't flip it end-for-end to use the ports in the proper orientation because then it would have to point forward and conflict with the oil filler, so it won't fit if you try to accomplish that.

Try an IAC from Ford...

choltz
11-24-2008, 10:23 AM
KMT,

OK, I'm still confused on the IAC thing. What do you mean the ports are opposite? Do you mean the solenoid is designed to move the opposite direction? As I said, I ran an aftermarket one for 10 years without problems and the one I just replaced looks identical inside and out. The new one did not have a pigtail connector. It did have the white bellows just like the one I took off.

I'm not trying to be hardheaded here, just trying to understand so that I can watch for this in the future.

choltz
11-24-2008, 10:36 AM
mywhite89,

The SPOUT code is an intermittent problem that I have. I hadn't been clearing the memory codes correctly (it's been years since I had to troubleshoot this thing!).

Anyway, I'm starting to think that the ECT might be the problem. I remembered something from a month or so ago that might have been the start of this idle problem. The radiator overflow was boiling over on the way home (I think some debris got caught in the radiator cap and so it wasn't holding pressure). Anyway, I unplugged the ECT to force the fan on continuous. That allowed me to get home. When I got home, I hosed off the engine compartment to clean out the antifreeze that had splattered everywhere. I'm wondering if some antifreeze and water got into the ECT connector and corroded it to where I've got higher resistance than I should. That would show up as the engine being colder than it really was according to the temp to voltage charts.

If the computer thinks the engine is cold, I would agree that it could cause hard problems when warm because it would be enriching the mixture, possibly to the point of flooding. Again, when this happens, I can put the pedal to the floor (flood clear mode) and it will fire, it just won't run.

The ECT was brand new back in the July timeframe. I had replaced the original radiator (kind of full of holes and solder!) and replaced both the ECT and the temp gauge sender at that time. After installing the new radiator, I did test that the fan was coming on at the right temp (~220) by holding a digital thermometer right next to the radiator, so I'm assuming the ECT was working properly then.

Maybe the ECT just plain failed which is why the car overheated that first time. I'll do some more testing on it and maybe put the old one back in (it wasn't necessarily bad, but thought it was a good time to do it). I was a little troubled by the fact that the new ECT from Oreilly's was all plastic instead of brass like the original, but that's just how most stuff is these days!

Keep the ideas coming, and I'll keep you posted.

Thanks,
Corbin

KMT
11-24-2008, 03:40 PM
KMT,

OK, I'm still confused on the IAC thing. What do you mean the ports are opposite? Do you mean the solenoid is designed to move the opposite direction? As I said, I ran an aftermarket one for 10 years without problems and the one I just replaced looks identical inside and out. The new one did not have a pigtail connector. It did have the white bellows just like the one I took off.

I'm not trying to be hardheaded here, just trying to understand so that I can watch for this in the future.

I'm just going on what that post tries to point out - I use FOMOCO part numbered IACs & have no IAC issues. Forget about your 10 year old IAC for now.

Let's say the two ports on a FOMOCO IAC are known as port A & port B. Port A is the one nearest the front of the car & port B is the one towards the rear. Same goes for the ports on the flange. Pretend we are looking down on the IAC from the top, with the front port A on the left.

When installed:
flange
A ~ B:
A ~ B:
IAC from Ford

The wrong IAC has two ports as well, but their operational abilities internally are opposite:
B ~ A:
IAC from aftermarket

When bolted on (the only way it will fit & with the housing oriented same as the IAC from Ford), the result is a mismatch:
flange
A ~ B:
B ~ A:
IAC from aftermarket

Without any other information on how to identify an incorrect aftermarket IAC, the only way to know that the IAC isn't part of things now is to get your hands on a Ford unit long enough to bolt it on and check how the car runs.

Since (1) the car runs at high idle with the aftermarket IAC in place and connected, but no high idle when unplugged and (2), other owners are warning against the use of aftermarket IACs... it seems logical that it is playing a role in your high idle.

>After installing the new radiator, I did test that the fan was coming on at the right temp (~220) by holding a digital thermometer right next to the radiator,
Why would you do that? 220 next to the radiator is overheating at the ECT.

>I'm wondering if some antifreeze and water got into the ECT connector and corroded it to where I've got higher resistance than I should

Bit of a reach - you're just chasing ghosts now.

Good luck with tracking down your issue(s).

TbirdSCFan
11-24-2008, 08:13 PM
As I said, I ran an aftermarket one for 10 years without problems and the one I just replaced looks identical inside and out. The new one did not have a pigtail connector. It did have the white bellows just like the one I took off. Then the new one is correct.. Hmmmm... did you check the throttle plate.. At this point, I'd say try swapping out the EEC. Especially since you say it passes the KOER test.

choltz
11-24-2008, 09:31 PM
Well folks, maybe not conclusive, but pretty darn close!

This morning I tried cleaning the ECT connector with alcohol and Qtips. On the way to work my 2500 RPM idle was still there. Note that this is a 19 mile drive with both highway and city driving, and it was idling high probably 1/2 the time. By the time I got to work, the temp gauge was getting awfully high, so when I parked I unplugged the ECT to force the fan on and cool the engine down before I shut if off.

I left the ECT unplugged for the drive home as an experiment, and the engine ran beautifully! When first started (cold) she idled at about 1000-1200 RPM (normal warmup), although you could see the idle hunting a little. As the engine warmed up and I was stopped at lights, you could see the computer lowering the idle, still hunting but definitely on the way down. I'm assuming the computer was trying to "learn" a good idle speed without temp knowledge. By the time I got to about the 3rd stoplight, the engine was idling around 700-750 RPM and I had no problems the rest of the way home.

I won't have time to swap the ECT until Thursday, so I'll just leave the ECT unplugged until then to make sure my problems are gone. Seems like a testament to the Ford engineers that the car runs pretty darn good without an ECT signal (certainly better than it's been running with what is apparently a BAD signal!).

Thanks for all the replies. Hopefully this thread will be helpful to others as well.

I'll post again after I replace the ECT to let everyone know the outcome.

Thanks,
Corbin

David Neibert
11-25-2008, 11:10 AM
Well folks, maybe not conclusive, but pretty darn close!

This morning I tried cleaning the ECT connector with alcohol and Qtips. On the way to work my 2500 RPM idle was still there. Note that this is a 19 mile drive with both highway and city driving, and it was idling high probably 1/2 the time. By the time I got to work, the temp gauge was getting awfully high, so when I parked I unplugged the ECT to force the fan on and cool the engine down before I shut if off.

I left the ECT unplugged for the drive home as an experiment, and the engine ran beautifully! When first started (cold) she idled at about 1000-1200 RPM (normal warmup), although you could see the idle hunting a little. As the engine warmed up and I was stopped at lights, you could see the computer lowering the idle, still hunting but definitely on the way down. I'm assuming the computer was trying to "learn" a good idle speed without temp knowledge. By the time I got to about the 3rd stoplight, the engine was idling around 700-750 RPM and I had no problems the rest of the way home.

I won't have time to swap the ECT until Thursday, so I'll just leave the ECT unplugged until then to make sure my problems are gone. Seems like a testament to the Ford engineers that the car runs pretty darn good without an ECT signal (certainly better than it's been running with what is apparently a BAD signal!).

Thanks for all the replies. Hopefully this thread will be helpful to others as well.

I'll post again after I replace the ECT to let everyone know the outcome.

Thanks,
Corbin

Corbin,

I've read this entire thread several times, and I'm convinced that it's the IAC valve that's causing your problems. The fact that the first one worked great for 10 years doesn't matter. 99% of the time they do not work. I just helped another member of this board fix the same problem a couple weeks ago. The fact that it idles down during self test or when you pull the ECT connection doesn't prove the IAC valve is working correctly. For example, if the IAC valve isn't able to lower the idle to the target rpm, the EEC will reduce the timing in an effort to lower it. Without hooking the car up to a scanner you have no idea what the IAC duty cycle is.

You can buy a used one for $20 and switch it in less than 15 minutes to verify if it is the source of your problem, or you can keep chasing electrical gremlins that may or may not be there.

David

XR7 Dave
11-25-2008, 07:45 PM
If disconnecting the ECT sensor helps the situation then I'd start by verifying that the cooling system is properly sealed and functioning correctly. Check this post for details on how. Link. (http://www.sccoa.com/forums/showpost.php?p=782149&postcount=8)

choltz
11-28-2008, 03:08 PM
Folks,

Thanks for all the replies. This morning I used my ohm meter to check both the old ECT (Ford original) and the "new" ECT that I have been running. At around 70 deg, the Ford unit was showing around 30K ohms and the new one was showing around 100K ohms. According to the ECT table in a book I have, the Ford one was in the right ballpark. The new one obviously is reading way to high (which translates to reading way cold).

I put the original ECT back in and took it for a drive. The car idles properly and had no problems. Even when it wasn't idling at 2500, it never dropped below 900 with the bad ECT in. Now it's idling around back where it should, 700-750.

In reality, I'm not sure if the ECT should ever fail. It's just a thermistor. The only reason I changed it in the first place was because I was in the area when I changed the radiator and put on all new hoses. I won't be doing that again!

On the IAC comments, I still don't see why everyone keeps pointing to it. If I unplug the IAC and the idle drops to around 600-700 (which means the IAC is seating closed correctly), and if during the KOER test (with the IAC plugged in) the engine is able to bring the idle down properly, why wouldn't you think the IAC was working?

Again, the conclusion here is that the EEC really was commanding a 2500 RPM idle for some reason, apparently because the ECT was showing that the engine was too cold. Maybe the issue is that all other sensor readings (ACT, O2, etc) were pointing to a warm engine and it caused a problem in the EEC strategy (whatever one it's in).

Some day maybe I'll figure it out. I'm working on designing an onboard diagnostic system using an Arduino microcontroller that will be able to monitor every signal going into/out of the EEC (I would have immediately been able to see that the ECT reading was too cold and that the IAC was receiving a command to raise the idle). That system along with the built-in diagnostic should make troubleshooting much easier!

Thanks again!
Corbin

XR7 Dave
11-28-2008, 04:11 PM
An interesting thing happens when you have a faulty ECT value. The amount of idle air that is commanded as a baseline to keep the car idling depends on engine temperature. This command is separate from the actual idle speed command and takes precedence. Due to added friction in a cold engine as well as reduced fuel atomization with a cold cylinder, more air is commanded to achieve the same idle as would be needed when the motor is warm. The EEC relies on this ECT value for setting up the entire idle strategy. If the engine doesn't actually have the friction that a cold engine would and is benefiting from proper fuel atomization in the cylinder, then the amount of air required for idle is greatly reduced.

I'm not sure if I'm making sense, but the point is that the EEC never commands a 2500rpm idle. Never. Instead, it was commanding a fixed amount of air that it thought it would need to achieve normal idle but since you don't need that much air, the idle skyrockets and then the EEC is not able to control it.

The EEC primarily uses spark advance to actively control idle speed. The IAC does do some learning, but the window is small and the response is slow. With your car idling at 2500rpm due to the extra air that it doesn't need, apparently 900rpm or so is the lowest that the motor could be brought down by pulling the maximum amount of timing from the motor + IAC learning routines. Normal idle spark is around 20-25 deg and typically minimum idle spark is somewhere around 0 deg.

You have experienced one of the funny (or maybe "odd" is a better word) and unexpected things that can happen when the EEC receives "garbage in" and in turn gives "garbage out".

fturner
11-28-2008, 04:24 PM
You have experienced one of the funny (or maybe "odd" is a better word) and unexpected things that can happen when the EEC receives "garbage in" and in turn gives "garbage out".

You are learning oh wise one.... You may yet become one with the silicon :D..

Dave has a point. In our computers, we can set a "target idle" we want the car at when everything is perfect, but there is alot going on before it gets there. Idle is controlled primarily with spark because it is faster. Air flow is estimated which tells the IAC a certain duty cycle for a "measured" amount of air coming in. The MAF reading is practically ignored because it is so slow to respond and the measurement is so low at idle levels so a "fixed" estimate has to be in place. As Dave mentioned, garbage in, garbage out, and that would really throw the "fixed" air amount wanted out to the dump if you have a bad sensor.

Frit

KMT
11-28-2008, 04:48 PM
The ECT is used to calculate fuel ratios and timing curves.

An ECT in that range (telling the EC that the coolant was at near 0 F.), would result in the EEC switching to a richer fuel strategy (along with altering timing accordingly) - what else happens before the EEC also starts commanding more or less air..? Is the IAC brought in at this point...?

The engine should have been acting as if it was flooded when it was both cold and hot started. An out-of-range code for the ECT should have been present as well I believe.

>Air flow is estimated which tells the IAC a certain duty cycle for a "measured" amount of air coming in.

He said the engine idled properly when the IAC was unplugged (w/the 'new' ECT) - how? ....when fuel should have been high rich?

fturner
11-28-2008, 05:54 PM
The EEC has code in it that can "adapt" to almost any sensor fail. If the IAC fails there are settings that says, ok, lets "assume" a setting and force that setting through the programming so the car can be driven until it gets to somewhere that can be fixed. In this state you can be positive the car will run rich.

For instance, on an IAC failure, the computer will assume a certain amount of airflow allowed through the TB to sustain an idle condition. Thats why I keep stressing that the TB idle be set up right without the IAC. Some folks seem to think that the car will not idle without IAC control and tell everyone so..... and that tells me they don't have a clue. A TB set up properly will allow a car to idle reasonably even when the IAC is unplugged, but hey what do I know :rolleyes:.

I won't get into details here, but if someone wants, I can show the numbers of what will happen. Least to say, the EEC coding is a marvel in programming and Microsoft could take a lesson in coding from the Ford engineers that wrote this stuff.

ECT is actually used in alot more than what you think it is judging from your post.

Frit

XR7 Dave
11-28-2008, 07:33 PM
He said the engine idled properly when the IAC was unplugged (w/the 'new' ECT) - how? ....when fuel should have been high rich?

No. The motor does not run rich when it is cool. It runs rich at first start up but that is all on a timer that counts down. The EEC goes closed loop (14.64 AFR) after about 15-90 seconds after which time the mixture would not be rich regardless of engine temperature. Federal EPA law required all cars (of the SC era) to run closed loop (14.64 AFR only) 90 seconds after start up. Newer cars have to reach closed loop even sooner. Some new cars even have a cold start "enleanment" to aid in converter light-off. Just because a motor is cold doesn't mean it will automatically be rich.

KMT
11-28-2008, 07:35 PM
>ECT is actually used in alot more than what you think it is

Perhaps. I'm aware that the ECT is a primary source of input - I also know that as many as four sensors can be taken out of play and the EEC will fill in the blanks.

>...force that setting through the programming so the car can be driven until it gets to somewhere that can be fixed.

I can work that out as well - of course it makes sense...but when no codes are detected (which limp mode should produce), I'm left to wonder what is actually happening. I work from the presumption that it is as much a mistake to troubleshoot without pulling codes as it is to ignore 11 11 when pulling codes and running issues are present.

>In this state you can be positive the car will run rich

Agreed - so where's the code...? Why would the EEC jump the shark and settle at 2,600 rpm (without any codes), which isn't part of any failure strategy I'm aware of. :confused::confused:

>EEC coding is a marvel in programming

A direct benefit from FOMOCO's aerospace division back in the day.

KMT
11-28-2008, 07:45 PM
>The motor does not run rich when it is cool.

Not my point

>It runs rich at first start up

That's my point. And we don't really know if any of his testing out-reached the timer(s) or not.

I'm just talking about how he proposed that the ECT (regardless of whether the coolant was cold/hot) was forcing a signal that should have triggered the engine to respond with increased fuel in the form of (1) more fuel and/or (2) less air...right? Lessen the air and the result is a rich(er) cylinder condition...no? We're just talking about starting conditions, not running.

As for running, I still can't work out how the engine raised the idle when the IAC was connected if the ECT was borked - and didn't when the IAC was disconnected. Something else is still not not known/not correct.

fturner
11-28-2008, 09:19 PM
Honestly, if one looks at error codes from the EEC to determine problems and call that gospel really needs to get their head examined.

The EEC will only call an error with something based on what it has been told is a problem. For example, the EEC will call an error with the BAP sensor when that sensor has reached a level that none of us can live in..... you want to go by that sensor reading??????

For a CEL to go off for ECT temps... guess what, you'd have a molten slug of iron dripping on the ground before you'd get a cel for an ECT failure, and that goes for ACT sensor as well.

To live your life thinking that your car is fine until the CEL goes off is only saying you have an issue that should be looked at.

Frit

KMT
11-28-2008, 09:40 PM
> Honestly, if one looks at error codes from the EEC to determine problems and call that gospel really needs to get their head examined.

No one here said anything different.

We're still left with the unanswered question as to why no codes surfaced in this case. Nothing wrong with that as a question :)

While trying to analyze these types of things over the internet can easily lead to mysteries (when it comes to the EEC), siding with voodoo isn't really an answer.

I can understand a 2,600 rpm 'idle' being a result of one or more component failures, but I can't make the reach that it would be part of any built-in failure mode/strategy.

choltz
11-28-2008, 09:40 PM
KMT,

As has been stated, it sounds like the EEC was using the IAC to get enough air into the engine for a cold idle, which for a hot engine was apparently enough to turn 2500 RPM under zero load. So when the IAC was plugged in, I got a high idle. Unplugging the IAC (which is spring-loaded to be closed when not commanded) just closed the IAC and got me to the amount of air needed for idling a hot engine (the idle setting on the throttle plate).

As a software engineer, I know from experience that "garbage in -> garbage out" is a software way of life. :)

I'm glad my struggles have produced such a great discussion on the bowels of the EEC!

Thanks again!
Corbin

fturner
11-28-2008, 09:53 PM
> Honestly, if one looks at error codes from the EEC to determine problems and call that gospel really needs to get their head examined.

No one here said anything different.

We're still left with the unanswered question as to why no codes surfaced in this case. Nothing wrong with that as a question :)

While trying to analyze these types of things over the internet can easily lead to mysteries (when it comes to the EEC), siding with voodoo isn't really an answer.

I can understand a 2,600 rpm 'idle' being a result of one or more component failures, but I can't make the reach that it would be part of any built-in failure mode/strategy.

Son, you really need to learn what software engineering is all about. The computer will only do what it is told to do and nothing else. Your looking for a CEL that will never happen. Take the BAP sensor, the EEC will not fail it unless your living on Jupiter..... care to test that for me ;).

There is no voodoo when it comes to what the computer will report. Why do you swear your diagnostics on a piece of silicone programmed by a human? I can think of hundreds of things that could cause a motor to crap out and it'll never throw a cel.

Have fun cel hunting :D.

Frit

KMT
11-28-2008, 10:02 PM
>Unplugging the IAC (which is spring-loaded to be closed when not commanded) just closed the IAC and got me to the amount of air needed for idling a hot engine (the idle setting on the throttle plate).

...with an out of range ECT influencing the system by reporting dead cold coolant...? Only if the system choose to ignore the ECT signal. An out of range ECT should normally produce an error code. The EEC would have been trying to control the unplugged IAC at the same time, which would have thrown another code.

Two codes simultaneously not thrown, yet the system is thought to be in failure mode? Something has to trigger the failure mode, which should toss yet a 3rd code. But you're reporting 11's. It is very hard to imagine that this represents a system in otherwise normal operation.

I think you still have issues - just my opinion, but hey, that's what forums are for.

KMT
11-28-2008, 10:04 PM
>Son, you really need to learn what software engineering is all about

Don't patronize me frit - I was coding when you were just a glint in your father's eye. I'll put my software experience and programming skills against anyone's.

Try to stay on topic - if you don't know the answer, it's ok to say so.

frdlvr30
11-28-2008, 10:20 PM
>Unplugging the IAC (which is spring-loaded to be closed when not commanded) just closed the IAC and got me to the amount of air needed for idling a hot engine (the idle setting on the throttle plate).

...with an out of range ECT influencing the system by reporting dead cold coolant...? Only if the system choose to ignore the ECT signal. An out of range ECT should normally produce an error code. The EEC would have been trying to control the unplugged IAC at the same time, which would have thrown another code.

Two codes simultaneously not thrown, yet the system is thought to be in failure mode? Something has to trigger the failure mode, which should toss yet a 3rd code. But you're reporting 11's. It is very hard to imagine that this represents a system in otherwise normal operation.

I think you still have issues - just my opinion, but hey, that's what forums are for.
An ECT sensor has no idea when it is out of range, to a certain extent. It uses resistance converted to a voltage value to indicate coolant temperature. Therefore, it simply thinks that the coolant is hot when it is actually cold or vice versa. It usually does not set a hard fault when malfunctioning. I say usually. I say this from my extensive driveability experience. No patronizing here....Not to say that I havent seen a ECT hard fault...I have. Just more oftem than not I would have to look at the ECT voltage in datalogging to verify that it was off/malfunctioning. This is especially true on GM vehicles as well.

KMT
11-28-2008, 10:44 PM
>An ECT sensor has no idea when it is out of range

Of course.

But the EEC does. And for the EEC to react as described, without codes, seems unlikely. Chalking it up to whimsy isn't much of an answer. That's all I'm saying.

>It usually does not set a hard fault when malfunctioning. I say usually.

Agreed - in those cases I would also expect the EEC to only introduce marginal trim values (elsewhere) and not have reason go to a failure mode, bypassing sensors entirely.

How can an extremely high idle be considered a 'safe' mode enabling the car to be driven in for repairs?

frdlvr30
11-29-2008, 01:06 AM
>An ECT sensor has no idea when it is out of range

Of course.

But the EEC does. And for the EEC to react as described, without codes, seems unlikely.
The EEc doesnt know either. Your missing the point here. The EEC is only as good as its inputs. Fuel control inputs being MAF, IAT, ECT, and HEGO's. If the ECT is reading 1.1volts it thinks its 100 degrees (example only). Thats all it has to go by to adjust injector pulse width/fuel trim for the starting calibration. It has nothing else to go by. If the sensor is not open or a complete hard fault, the EEC has no idea that there is a problem. You are looking way to deep into this. EEC-IV is not as complex as you are giving it credit for...I can assure you. EEC_V is much more complex. It is very possible and likely to have sensor input malfunction without CEL on. Believe me there were many times when I wished it wasn't possible. Reading codes and swapping parts would have been much easier. Your last sentence that I have quoted above could not be further from the truth. It is very likely....

frdlvr30
11-29-2008, 01:15 AM
How can an extremely high idle be considered a 'safe' mode enabling the car to be driven in for repairs?[/QUOTE]
These cars are not programmed for any kind of safe mode. If your car is idling at 3k rpm's. Your supposed to have enough common sense to call a tow truck...that simple. A cars particular reaction to certain faulty sensors and sequences was never planned I can assure you.

KMT
11-29-2008, 01:38 AM
>If the sensor is not open or a complete hard fault, the EEC has no idea that there is a problem.

Again, I agree - which means I dispute the previous posts that claim the ECT caused the car to drop into failure mode...the car isn't in failure mode.

>These cars are not programmed for any kind of safe mode. - A cars particular reaction to certain faulty sensors and sequences was never planned I can assure you.

While they are programmed for safe/limp/failure management (Failure Management Effects Mode*), thanks for the agreement concerning such a ridiculously high idle - and since I'm the one pointing that out, please direct your assurances to those that tied the two together in the first place, not me :)

*98 Hard fault present. The PCM is running in FMEM (Failure Effects Management Mode)

frdlvr30
11-29-2008, 01:42 AM
>If the sensor is not open or a complete hard fault, the EEC has no idea that there is a problem.

Again, I agree - which means I dispute the previous posts that claim the ECT caused the car to drop into failure mode...the car isn't in failure mode.

>These cars are not programmed for any kind of safe mode. - A cars particular reaction to certain faulty sensors and sequences was never planned I can assure you.

While they are programmed for safe/limp/failure management (Failure Management Effects Mode*), thanks for the agreement concerning such a ridiculously high idle - and since I'm the one pointing that out, please direct your assurances to those that tied the two together in the first place, not me :)

*98 Hard fault present. The PCM is running in FMEM (Failure Effects Management Mode)I did not read the entire thread, sorry.
There is nothing safe about FMEM....just means that you may or may not be walking

KMT
11-29-2008, 01:44 AM
I did not read the entire thread, sorry.
There is nothing safe about FMEM....just means that you may or may not be walking


I've always called it 'limp' mode (because you limp home, if at all), and only adopted the term 'safe' from users here :rolleyes:

Pacman
11-29-2008, 10:05 AM
I had almost the exact same problem with one of my sc's and it would give me a spout failure code intermitently. Tried the dis off my other sc and it ran like new again! Try the dis, I put the bad one on the other car and it ran the same way, so i bought one from the salvage for $15 and had two running cars again.

fturner
11-29-2008, 11:15 AM
>Son, you really need to learn what software engineering is all about

Don't patronize me frit - I was coding when you were just a glint in your father's eye. I'll put my software experience and programming skills against anyone's.

Try to stay on topic - if you don't know the answer, it's ok to say so.

I'm not going to get involved in a pissing contest with you as to who is the better programmer as that is not what this forum is about. I am very confident in my skills and knowledge I don't need to brag about it, but just remember, there is always someone that is better than you are.

Go ahead and advise the person on how to solve his problem as you seem so sure you are 100% right.

Have fun :D.

Frit

Torino Cobra
11-29-2008, 03:58 PM
Wow you guys are so serious!

mywhite89
12-01-2008, 08:40 AM
I had almost the exact same problem with one of my sc's and it would give me a spout failure code intermitently. Tried the dis off my other sc and it ran like new again! Try the dis, I put the bad one on the other car and it ran the same way, so i bought one from the salvage for $15 and had two running cars again.

I'll try this on my car and see what happens, I've got an extra DIS laying around. Gotta wait till the snow goes away before I can drive it a couple days though. It is just what you describe, an intermittent spout code.

Chris

KMT- You tune with SCT software?

TbirdSCFan
12-01-2008, 03:29 PM
I was coding when you were just a glint in your father's eye. I'll put my software experience and programming skills against anyone's. You young whelps. And I'll put my PDP8 toggle switch skills up against anyone here.. in Octal to boot, not this easy to read fancy Hex stuff. ;) :D

fturner
12-01-2008, 03:47 PM
Heck I've coded systems using punch cards and tapes.. I just realized I've been doing this computer programming crap for 30 years now....

Time to get out :eek:.....

TbirdSCFan
12-01-2008, 05:05 PM
The PDP8 had no OS. The octal codes were machine codes inserted into memory slot 0 in 1K of core memory. They defined a simple boot loader which would load another boot loader that would then load the application from mylar tape ;) You toggled the bits (in octal) and when you were done, hit the cpu restart (NMI) and let it go. If you messed up, it didn't go and you started over again. :D

KMT
12-01-2008, 05:57 PM
I'm not going to get involved in a pissing contest with you as to who is the better programmer as that is not what this forum is about. I am very confident in my skills and knowledge I don't need to brag about it, but just remember, there is always someone that is better than you are.

Go ahead and advise the person on how to solve his problem as you seem so sure you are 100% right.

Have fun :D.

Frit

I'll try one last time :)

If you don't know the answer to how this particular issue played out, it is ok to say so - but please don't try to snow people by claiming voodoo is at work...that's just a cop out.

If you look to be the go-to guy for tunes in the future, you'll face much harder questions than these, and telling customers the whole process is mysterious will only wash for so long.

I honestly don't know what went on, I'm admitting that and I'm simply trying to puzzle it out. Hopefully I'll learn something :)

KMT
12-01-2008, 06:15 PM
>You tune with SCT software?

My 1990 SC keeps me in the dark ages when it comes to tuning... We have an AWD Porsche that allows quite a bit more freedom, however. All OSS in that case.

If it runs on Windows only, you won't see me using it unless I'm paid - a lot - by the hour :)

fturner
12-01-2008, 07:37 PM
Thanks KMT, you just shutdown what I was hoping to start up with tuning services for people. Now everyone is going to think all I will be doing is snowing them.

You really should learn how the software in the EEC works, and you'll see that what I'm saying is fact, not just "voodoo".

Much appreciated.....
Frit

89XR7TD
12-01-2008, 09:56 PM
Well folks, maybe not conclusive, but pretty darn close!

This morning I tried cleaning the ECT connector with alcohol and Qtips. On the way to work my 2500 RPM idle was still there. Note that this is a 19 mile drive with both highway and city driving, and it was idling high probably 1/2 the time. By the time I got to work, the temp gauge was getting awfully high, so when I parked I unplugged the ECT to force the fan on and cool the engine down before I shut if off.

I left the ECT unplugged for the drive home as an experiment, and the engine ran beautifully! When first started (cold) she idled at about 1000-1200 RPM (normal warmup), although you could see the idle hunting a little. As the engine warmed up and I was stopped at lights, you could see the computer lowering the idle, still hunting but definitely on the way down. I'm assuming the computer was trying to "learn" a good idle speed without temp knowledge. By the time I got to about the 3rd stoplight, the engine was idling around 700-750 RPM and I had no problems the rest of the way home.

I won't have time to swap the ECT until Thursday, so I'll just leave the ECT unplugged until then to make sure my problems are gone. Seems like a testament to the Ford engineers that the car runs pretty darn good without an ECT signal (certainly better than it's been running with what is apparently a BAD signal!).

Thanks for all the replies. Hopefully this thread will be helpful to others as well.

I'll post again after I replace the ECT to let everyone know the outcome.

Thanks,
Corbin


He said his problem was solved why do you guys still beat each other up???

Tom