Its a screamer!!!!

[Green92LX]

I have a 89 notch with 200K plus as well as the 92 in my sig. Of course, the trusty old coupe runs like a bear, except for one problem.The problem is with the screamimg idle. It will be fine for a day or so, then out of nowhere the idle screams up to about 2 grand or so. The two ways I get it to go back down are to flick the key so it stalls and re-starts without the starter, or to go under the hood and unplug the IAC motor. So, if i reset the idle, it does not help either. In a few minutes, it hauls a@# back up to 1500 or around there. I changed the IAC and it did not help as well as the TPS. I do get a check engine on and off, but no patterns. Any ideas?


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1992 5.0 LX, Edelbrock 6037 Heads, Cobra Intake,E-303, 1.6 Rollers,65MM Holley TB, 75 MM Pro M Mass Air, 190 LPH FP w/ 24 lb injectors,BBK equal length shorties,offroad h-pipe,Mac Flowpath, Pro 5.0, 3.73's, subframe connectors

[QuantumMotorsports]

I have that exact problem on my cougar. I'm running an 88 speed density five speed computer and I'm almost convinced that is the problem. I got the computer really cheap off of ebay and the guy said nothing was wrong with it, but I've changed TPS, IA bypass valve and motor, cleaned the TB, checked codes, I get no codes even when the damn thing is idling high. The weird thing is when it's idling high and I test the codes, as soon as the scanner tells it to start test, it idles exactly where the computer wants it to for the test, then when the test is over, it goes low for a few minutes, but after driving it it's back up again. I'm almost positive it's the computer so I'm gonna convert to mass air and see if the new computer helps. Only other thing I can think of is a ground problem I've got. My ground strap from my computer to the chassis is kinda ghetto and worn from removing the computer so much. Anyway, if you find out anything be sure and post. I'll do the same.

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Michael Black
Quantum Motorsports
Norman, Oklahoma

1988 Merc Cougar 5.0 HO, P&Ped heads, 2.25" custom mandrel bent dual pipes, T5 five speed tranny
15.43 @ 91.08mph (not shabby for a 3600 pound car)
60' 2.453 Street tires suck!!!

[Green92LX]

You think it's a ground to the computer problem? I'm up for doing anthing to solve the problem, but that seems kind of sketchy.

Check for vacuum leaks. Yeah and if your electrical system doesn't have all of its grounds the EEC does some wierd things.

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88GT stock shortblock, ported GT-40 iron heads, ported Edlebrock Performer intake, 24# inj, Pro-M 75mm Bullet MAM, 3.73, hurst short throw, F-303, electric fan, alum rad, FMS HD clutch, R134a ac conversion, 70mm TB , and some other stuff I probably forgot, best run so far on ET streets is 13.02@106 with a 1.87 60ft.

[QuantumMotorsports]

I'm thinking it's not vacuum, but I'm not sure, reason I think it's not is because when you unplug the IA bypass motor it idles low. Is there some reason a vacuum leak would cause that? Does anyone know of a place to get a wiring diagram that shows location of grounds in the car? I also think it might have something to do with the TPS because sometimes adjusting the TPS will help for a while. I did notice that when you take the TPS off of the TB and twist the sensor like your stomping on throttle it revs the engine for you. I didn't realize the computer would open up the IAV when you stomp the gas. That is why I'm thinking it's TPS. Anyway, tell me what you guys think.

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Michael Black
Quantum Motorsports
Norman, Oklahoma

1988 Merc Cougar 5.0 HO, P&Ped heads, 2.25" custom mandrel bent dual pipes, T5 five speed tranny
15.43 @ 91.08mph (not shabby for a 3600 pound car)
60' 2.453 Street tires suck!!!

The reason I think it is a vacuum leak is because my sister's boyfriend has a Bronco with a 302. I cleaned the throttle body and lubed the throttle cable, cleaned the IAC, and adjusted the TPS. Still no fix. So I go to work with the carb cleaner when the engine is running. I noticed a difference in the idle when I sprayed it between the upper and lower intakes. I poked at a piece of gasket that was sticking out and it changed idle again. So I changed the gasket between the two and it idled fine from then on.

[my name is mud]

Hey GREEN92LX, I had the same problem in my 88(speed density)mustang, I replaced my TPS,IAC(when I disconnectd it it idled a little low but otherwise okay),all vacuum lines(I found some leaks but fixing them didn't help),MAPS sensor,cleaned my EGR and TB and I am sure I have forgotten some things, and my car would still idle at 2000 rpm, then I cleaned up the 10 pin connectors on the back of the intake(by the TB) and my problem was solved. If its not that connection try cleaning some other connections and the ground straps(I don't even know where they are though).

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88 mustang lx ragtop pulley's and a k+n
14.8 at 93mph

[QuantumMotorsports]

Hey mud! I thought something like that might be the prob. that's what I hate about most electrical problems, they intermittent and you can't ever figure out what the heck is going on. Hey, where in OK you from? Ever hang out in Norman or OKC? We'll have to line up and run em sometime for kicks. Thanks for the help.

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Michael Black
Quantum Motorsports
Norman, Oklahoma

1988 Merc Cougar 5.0 HO, P&Ped heads, 2.25" custom mandrel bent dual pipes, T5 five speed tranny
15.43 @ 91.08mph (not shabby for a 3600 pound car)
60' 2.453 Street tires suck!!!

[my name is mud]

QuantumMotorsports/Micheal Black, yeah electrical problems are a pain, and I hope you get yours worked out soon(sounds like you will). I live in northwest OKC,my real name is Burke, after the roads clear up some a race sounds like fun, just email me at lucas5@swbell.net, and you will have to tell me about you're cougar, I have never seen/heard of one with a T-5, sounds like an uncommon car, did you put that in yourself ? A haynes/chilton's manual would have the wiring diagrams, I might be able to fax you one for a mustang actually, if it would help.

[SHaFT7]

i had the same problem on my 91 GT and i took off the air intake hose right where it goes into the throttle body and cleaned the butterfly and the area right around that, and it went back down to normal

2 days later it started going back up, so i guess i didn't get all the deposits...next step = injector cleaner in the gas tank

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SHaFTed

[Green92LX]

Thanks mud, I'm at work right now, but I will definitely look at those connections when I get home. Also, I do have a small vacuum leak on the passenger side strut tower in that mess-o-hoses near the firewall that I cannot seam to locate. I will check on the electrical first, though. I will let you know what happens. Wish me luck!!!

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1992 5.0 LX, Edelbrock 6037 Heads, Cobra Intake,E-303, 1.6 Rollers,65MM Holley TB, 75 MM Pro M Mass Air, 190 LPH FP w/ 24 lb injectors,BBK equal length shorties,offroad h-pipe,Mac Flowpath, Pro 5.0, 3.73's, subframe connectors
Daily driver: 89 notch with 200K plus...and it runs like a champ.

[SHaFT7]

just a note.......aren't the 5.0's sequential multiport FI ?

91GT here

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SHaFTed

[QuantumMotorsports]

Hey Shaft, I guess I'm missing your point. The 87-95 stangs are SEFI. Don't mean to seem rude, but, so what?

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Michael Black
Quantum Motorsports
Norman, Oklahoma

1988 Merc Cougar 5.0 HO, P&Ped heads, 2.25" custom mandrel bent dual pipes, T5 five speed tranny
15.43 @ 91.08mph (not shabby for a 3600 pound car)
60' 2.453 Street tires suck!!!

[Green92LX]

Hey Quantum, I have good news!!! Tonight was the first chance I had to get under the hood. I found a vacuum leak on the passenger side near the strut tower, and I fixed it. Also, I set the TPS to 1 volt, it was at about .9 or so. The last thing I did was take apart the 10 pin connector and clean it up. Let me tell you, the car runs as smooth as a baby's a$$ now, and the idling problem is gone. I'm not sure which one of the items above it was, but I think it was the vacuum leak merely because I still have a check engine light. But my car just turned 205K and runs better than ever. Thanks to everyone for your advice and I hope this can help you Quantum.

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1992 5.0 LX, Edelbrock 6037 Heads, Cobra Intake,E-303, 1.6 Rollers,65MM Holley TB, 75 MM Pro M Mass Air, 190 LPH FP w/ 24 lb injectors,BBK equal length shorties,offroad h-pipe,Mac Flowpath, Pro 5.0, 3.73's, subframe connectors
Daily driver: 89 notch with 200K plus...and it runs like a champ.

[Green92LX]

Hey Quantum, I just wanted to post again to make sure you saw the solution.....

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1992 5.0 LX, Edelbrock 6037 Heads, Cobra Intake,E-303, 1.6 Rollers,65MM Holley TB, 75 MM Pro M Mass Air, 190 LPH FP w/ 24 lb injectors,BBK equal length shorties,offroad h-pipe,Mac Flowpath, Pro 5.0, 3.73's, subframe connectors
Daily driver: 89 notch with 200K plus...and it runs like a champ.

[QuantumMotorsports]

I saw your post, although I'm not sure which one of those it was that fixed it. I'll check it out. It's been a while since I've had the prob again, but I'll see what I can find. Thanks.

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Michael Black
Quantum Motorsports
Norman, Oklahoma

1988 Merc Cougar 5.0 HO, P&Ped heads, 2.25" custom mandrel bent dual pipes, T5 five speed tranny
15.43 @ 91.08mph (not shabby for a 3600 pound car)
60' 2.453 Street tires suck!!!

[SHaFT7]

my last post didn't have anything to do with this topic exactly, i was just wondering if they did.....



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SHaFTed