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archerman0531
02-08-2013, 08:57 PM
So, ever since I bought this car(1990 cougar xr7) it has always idled high(1500rpm for about 10-12 seconds, and that varies) and then goes down to around 1000-1100 rpm. When driving and push the clutch in it also revs higher to the 1500rpm range. How do I adjust the idle? The throttle stop screw was adjusted to were it wouldn't hit the stop. I adjusted it to where it actually rests on the stop. I don't see anything else for an idle adjustment. After its up to opp temp. It likes to elevate a couple 100 rpm and die back down and back up for a while almost like surging but not as exagerated, and finally settles down to 1000-1100. You can watch the vacuum/boost gauge waiver from 21-22 inch/lbs at 1000-1100rpm to 16-18inch/lbs as it increases in rpm.

Any help would be greatly appreciated.

I'm thinking possibly MAF, TPS, or IAC.

shoalcracker
02-08-2013, 09:41 PM
The TPS Sensor should be able to compensate some.

Very small rotation will change the voltage with I think a window of 95-120.

Do some searching and it will probably make more sense than my explanation.

Paul

archerman0531
02-09-2013, 12:17 AM
Thanks for the info, do you mean 95-120rpm? How is base idle set? Or is it by the ECM?

Scott Long
02-09-2013, 12:18 AM
vac leak sucking in un-metered air causing it to rev higher but it is going to cause a lean condition. I had a vac leak so bad on my SC once that it idled high and got the headers glowing red. that scared the hell out of me.

archerman0531
02-09-2013, 12:19 AM
Yea, I checked for vacuum leak(used a fogger) and appeared to be no leaks

Scott Long
02-09-2013, 12:23 AM
hmmm. i ripped mine back down to the intake manifold, resealed everything. I put teflon gaskets on the IC pipe connections, and got a new hose with some extra length for the PCV to SC plenum connection that kept popping off. After that mine idled good.

archerman0531
02-09-2013, 12:29 AM
Well, I'll refog it and see if I can maybe come up with something, because i first believed it was a vacuum leak as well because it takes forever for the Rpms to come back down if you flip the throttle. About 4 seconded to come down from the 2500rpm, sticks at 15-1700 for about 10-15 seconds, drops down to around 1200 and slowely ideals down to the 1000 rpm. Once it hits 1000 it will stay unless you flip the throttle again and it does the exact same thing over. So I'm stuck as to what it could be. Maybe the ECM needs to have the idle rpm adjusted? I'm not for sure if that's where idle is controlled from, i know in my f150 it was.

Also the whole top end has been rebuilt in the last 700 miles. And appears to have new gaskets for the intake manifold, as well as the IC Teflon gaskets

Scott Long
02-09-2013, 12:32 AM
there is a value in the EEC for base idle, and it can be adjusted, but if you've never messed with it, then there's no reason to believe it has been altered. Anything from the point of the mass air flow sensor forward has no effect on idle. Anything after the mass air flow sensor will be air extra air coming in that the computer isn't compensating for by adding fuel. If it's post throttle body it will cause the engine to idle higher, or "hang" like you are describing.

archerman0531
02-09-2013, 12:36 AM
Ok, thanks for the info, guess ill be looking for leaks tomorrow!

Scott Long
02-09-2013, 12:38 AM
check the lower IC tube to IC connection and tighten it up with a 13mm wrench (ratcheting wrench is a god send for the left nut on the stud). Also check the vacuum connection on the rear of the supercharger inlet plenum behind the throttle body. Check the passenger side valve cover under the throttle body where the PCV connects to this stupid plastic junction.

archerman0531
02-09-2013, 12:44 AM
Will do. Thank you

90sc35thann
02-09-2013, 06:59 AM
vac leak sucking in un-metered air causing it to rev higher but it is going to cause a lean condition. I had a vac leak so bad on my SC once that it idled high and got the headers glowing red. that scared the hell out of me.

X2 to this. You're pulling air from somewhere.

RSC'91
02-23-2013, 03:02 PM
I do hope you will post when you find the problem. I've had this issue almost exactly since I bought my '91 with 61,000 miles last year. Lowered it, painted it, put wheels n tires on it, put head gaskets in it, and its now sitting under a car cover in the driveway cause ive never been able to figure it out and gave up on it. Bought a '90 with 199,000 miles on it, put head gaskets in it and drive it daily. Ready to sell the red one cause I cannot stand the idle problem. Fogged, replaced every gasket from the block up, IC tubes, intercooler, the works... I wish you the best of luck and will be watching eagerly for your fix.

archerman0531
02-23-2013, 11:57 PM
I haven't found the problem yet. My guess is a sensor. I know all vacuum lines are good. Has GREAT vacuum. Boost to the approx. psi ad keeps it there. My guess is an ECT sensor being out of range or possibly a mixture of the MAF, TPS, an IAC. I haven't done much if anything to it lately except drive it. It drives great and gets great gas mileage still(27hwy). And it's just been to cold to be working outside on it. My ford truck had the same problem, and then got to where it wouldn't even idle all thanks to the ECT sensor reading that it was way colder than the actual air temp. Making a rich condition. I'm thinking this would do the same thing.
If it were the ECT that would also explain the hanging idle and the surging. ECT is going to ALSO control the TPS to some degree. Reading that it needs more air and fuel it will create the rich mixture and open the throttle, the o2 sensors are going to see this and realize that it is running rich and stop fuel flow, thus creating your "surging" idle.


it could also be the MAF sensor getting false readings(more air than what is actually being brought it, or a "surge" of air). I found this problem out with the newer mustangs that people put cone air filters(i do not have on tho) on with out a air box. When the cooling fan would kick on it would make the MAF read more air volume than there actually was, giving it more gas, makeing the car surge and coming up in the live datastream as a rich mixture setting off the check engine light. Being that our cars don't have quite the ECM the newer mustangs have, I'm gonna start with the ECT sensor.

Also my temp gauge is erratic, furthering my suspension of this sensor.

If someone thinks other wise, please let me hear your input. Thanks.

RSC'91
03-01-2013, 08:46 PM
I suspect the ECT has something to do with the issues I've had, when the car is at or above operating temp (hot Vegas days) it will cut out near to 4,000 rpm as if it were governed while under wide open throttle. If I would unplug the ECT it would run right up the rpm range as normal, however, the idle was non existent and erratic. I replaced the ECT brand new with no change, I replaced the thermostat with both a 180, then a 160 which only heat soaked the radiator, then back to the 192. I read here that new IAC valves (aftermarket) caused more problems than they were worth, so I replaced mine with two different valves from our local pick a part. Same result, no change. I replaced the MAF with a used one as well which also nettted little to no change. Really open to any suggestion cause its about ready to go down the road and it is truly a beautiful car. On a side note, the fuel gauge has never worked above the 1/4 mark even after a new pump/sender/tank, and gauge (well the gauge was used) I suspect this car has a hidden wiring issue that is causing these problems. There are just soo many to check...

archerman0531
03-02-2013, 11:02 PM
So, today I changed out the temp sensor and replace the thermostat since I was there any way and it needed replaced. Took almost 60 miles for me to get descent warm air.
I replaced it, and great hot heat now, and temp gauge works. I found that the SC belt had rubbed completely thru 1 wire of the crank sensor wiring harness an was on its way to go thru the other 2 that was in the loom. I spliced the wires back and rerouted the harness so it wouldn't happen again!

After this the car started kicking down the idle to about 1000 and didn't rev up to the 15-1700rpm range. I can push in the clutch and the rpm drops as it should but still not to the 800rpm range. If your at a stop light for a bit it still kinda revs up an down. 1000 rpm to bout 1300, and then back down and back up, and does this for about 20 or so seconds and finally just summers down and stays at the 1000rpm range. And slowly ideals to about 900.

After repairing the wiring my tach is even more intermittent working and not working.

I still don't know what is causing the "surging".

Any other input on the subject would be greatly appreciated. I'm thinkin maybe the iac. Does anyone have the values for checking it?(ohm resistance or volts?"

Thanks

RSC'91
03-16-2013, 02:13 PM
A jumpy tach sound a lot like a bad cam sensor, or at least one that is on its way out. Good luck on the specs, i've seen them posted here but cannot remember who put them up.

archerman0531
03-16-2013, 04:07 PM
I thought the tac was ran off the crank sensor?

TbirdSCFan
03-16-2013, 06:24 PM
I thought the tac was ran off the crank sensor? It actually taps off the DIS module. But the cam sensor typically makes this happen. The DIS itself can also cause the problem.

With the idle surge, Id double check the IC tubes and for any vac leaks. Suspect areas are anything that was touched during a recent repair. IC tubes and the SC top, and especially where the return IC tube attaches to the intake. If you did work around the dash, theres vac lines for the AC, the boost guage, and the cruise control.

After that, theres the IAC itself. Not a bad idea to have a spare. Also, if anyone monkeyed with the throttle stop screw, slap them. The throttle plate should be closed lightly with no throttle. The EEC controls the idle through the IAC. Its not uncommon for people to mess with it when trying to fix low idle.

archerman0531
03-16-2013, 08:53 PM
Well I've checked and checked for leaks and have had it smoked. Everytime shows up nothing. I'm fairly confident in the person that did the work as well. I'm a ford tec and I worked with the older guy that did the work, and he's pretty good around a sc. But I quite working there so I haven't had him look for any other problems as its $95 labor hour.

I notice right after I bought it that the throttle would stick if you let it slap back, like the blade would almost wedge in the bore, I noticed that the throttle stop screw was adjusted so far out that the screw didn't even touch the throttle stop plate. When I replaced the coupler in the supercharger I tightened the screw to we're it made contact with the throttle and twisted the screw about 1/2-3/4 turn further so I could see the blade barley open.
It hasn't affected the idle by keeping it higher. And since I've replaced the temp sensor my idle has been down more, and it seems the warmer it gets out the quicker it seems to idle down, but still not right. And the way it idels an surges varies from day to do.

I haven't had the time take the iac off an block it off and see what that shows.

I sealed the IC top tube to the intercooler when I replaced the coupler

The car has had the head gaskets replaced, supposedly they also milled the heads. I have the paper work showing the work done.

after driving The car in town whenever you push the clutch in it jumps to 2k and stays there for almost the entire time when sitting at a stop light.

It's just annoying having it idle so high just sitting there.

gr8ghost
03-17-2013, 02:58 AM
If you unplug IAC at hot idle, it should cause the car to stumble or die. Have you tried unplugging it?
Resistance is >10,000 ohms from either terminal to the case. resistance between terminals should be 6-13 ohms. Be sure the ohm meter is connected red lead to the red wire's terminal and the negative to the wht/lt blu wire's terminal on the IAC. There's a diode in there. So if you hook the ohm meter up backward it should be infinite resistance. Voltage to the VPWR terminal should be 10.5 V or higher. Ideally it should be the same as the battery voltage. The voltage between whit/blue and black (pwr grnd) should vary 3-11.5 volts when revved up from idle to 300 rpm.

Does your check engine light come on? if so read the codes. If all the above are ok check the throttle and CC cables for binding, throttle body for contamination, Iac gasket leak, and finally back to your old nemesis vacuum leaks. Put a vacuum pump on it at entrances to different systems like the CC, heating and AC, and power brakes to name a few.

PS Idle is spelled idle. Sorry it's the English teacher in me.

gr8ghost
03-17-2013, 03:05 AM
Be sure the canister purge (CANP) solenoid is not stuck open.

TbirdSCFan
03-17-2013, 03:16 AM
after driving The car in town whenever you push the clutch in it jumps to 2k and stays there for almost the entire time when sitting at a stop light. 2k idle is usually from a perforated bellows in the IAC. My 5speed did that too. I bought a new IAC and that fixed it. Used IACs might be OK, but the nylon bellows gets brittle, so you dont know how long it'll hold up.

archerman0531
03-17-2013, 10:30 AM
No check engine lights on at all unless I unplug the MAF. When I unplug the IAC it actually idles down nice....for a while and then slowely goes back to its original idleing. If I unplug the MAF it does stumble and almost dies, but corrects itself and idles descent and at a lower rpm, but misses.

I need to take the IAC off and look at the bellows.

I hooked up a traditional vacuum gauge to it and it reads steady at 22 in/lbs when it idles at 1500. When it finally drops to around 1000 the gauges shows around 18in/lbs. the needle on the gauge diesel flicker and it's not erratic, just a nice steady hold and drop once it decides to kick down.

archerman0531
03-17-2013, 10:31 AM
Where exactly is the canister purge solenoid located?

gr8ghost
03-17-2013, 12:05 PM
You said in there that the tach is erratic, As well. Like there is a problem other than the high idle speed. I chased bad wiring on mine for months only to come up empty handed. I spoke to the ford mech and he said, "It's likely the tach itself. Erratic tach behavior is almost always the tach." And you know what? He was right.
So if you check the ICM, the Cam sensor, the ground system (especially the engine ground on the R side and the instrument panel ground), and the wire to the tack and it's all good, replace the tack.

gr8ghost
03-17-2013, 12:16 PM
Where exactly is the canister purge solenoid located?
It is located behind the R headlight, under the fender. It will be easy to see if you go from under the car or remove the R inner fender cover. It should have vacuum supply to it ( make sure that circuit doesn't leak) and have 30-90 ohms resistance.
Also do check IAC valve that it does not leak. Take it off and try to blow and suck air through it. Make sure your girlfriend doesn't catch you. She might get jealous.;)

archerman0531
03-17-2013, 07:01 PM
Ok, so today I had a bit of time, so I pulled the iac off and blocked off where it mounts, started it up and it died almost instantly. I tried again to start it and it almost wouldn't start.

I even plugged the iac in with it dismounted from the TB and it didn't move at all when I tried to start it.

I checked the canister, it's within range, and no leaks there. I'm going to be buying an iac this week I guess unless someone thinks of something else it could be.

TbirdSCFan
03-17-2013, 09:47 PM
That should fix you up. Be sure you get one that is the same as the original. Some years back, "they" tried to pawn off this contraption that had to be mounted backwards. :rolleyes: The right part has a white bellows. Thats what they look like before wear. Don't touch anything inside of it.

archerman0531
03-17-2013, 10:27 PM
Hopefully it will be the right one. I bought it off eBay it's an ac Delco. Motorcraft was so expensive. $115. Ac Delco was $35. And yes I know you get what you pay for, but I'm willing to go cheap right now and replace as needed.

gr8ghost
03-17-2013, 11:26 PM
Sounds like you found your problem. Why don't you go to a local autoparts store and buy one. These are common parts. Ford put them on everything, practically. I hope yours works. We like to think of our cars as special. The truth is other than the Blower they are Fords. Ford put many of the same parts on many cars that had fuel injection and distributorless ignitions. So you don't always have to go special ordering stuff just because it's an SC. I find that easier. So if there's a problem, I take it right back.

archerman0531
03-17-2013, 11:53 PM
I know that some parts interchange between cars, only reason I got it off ebay was because the ford dealership that's in town was high priced for it, an that's even with a discount from them because I used to work there(ford cert. tec) but, the gm was kinda out there and started giving me less and less jobs, so I just quit and got me another job. But I kept in touch with everyone. So now I get breaks on labor and parts still
Ill find out wendsday or Thursday if the part worked!

TbirdSCFan
03-18-2013, 01:03 AM
Both are name brand, so you should be fine. Just dont go poking inside it to clean or otherwise.. Take a guess as to why I say that ;)

archerman0531
03-18-2013, 01:18 PM
Inside the TB? Or IAC?

I know some TB are not supposed to be cleaned because the sludge inside it helps it work correctly, they have a name for it, I just can't remember what it is.

First thing. Idk why someone would clean inside a brand new IAC...anyway, I would guess there are seals you could damage at the front of the accordion, or somehow mess up the bore it slides in, and not to mention the actual accordion would be easy to damage.

Lmk if that's right or if there's another reason

gr8ghost
03-18-2013, 08:49 PM
Inside the TB? Or IAC?

I know some TB are not supposed to be cleaned because the sludge inside it helps it work correctly, they have a name for it, I just can't remember what it is.

First thing. Idk why someone would clean inside a brand new IAC...anyway, I would guess there are seals you could damage at the front of the accordion, or somehow mess up the bore it slides in, and not to mention the actual accordion would be easy to damage.

Lmk if that's right or if there's another reason

Amen Brother. There's no reason to clean and new one.

TbirdSCFan
03-19-2013, 01:07 PM
Idk why someone would clean inside a brand new IAC...anyway, I would guess there are seals you could damage at the front of the accordion, or somehow mess up the bore it slides in, and not to mention the actual accordion would be easy to damage. Thats correct, but some of us may have monkeyd with an older one and learned how brittle that accordion can get. :rolleyes: :D

archerman0531
03-19-2013, 01:39 PM
Oh I see, a little first hand experience here! Lol

archerman0531
03-21-2013, 08:33 PM
Got the nex IAC in the mail today. Put it in(disconnected the batt for 15 min) And it idles as it should now!

Thanks for all the input and help!!