I replaced the EGR tube today in hopes that my 1500-2000 idle would go away after confirming a leak in the old tube. But its still there! I have replaced every sensor, all the ignition components, resealed every gasket, replaced vacuum lines, and cleaned TB with throttle cleaner. BUT THE DAMN F'd up idle won't go away.

Symptoms were and still are: High idle 1500 at startup.
2000 with heater on.
occasionally start up will be 800 until I drive.
Idle will settle to 800-900 after about 2-3 minutes sitting after driving.
I don't get it. I have donr everything possible, but I still have a bad idle. What the hell is wrong?

Oh NO......you're a long way from everything..........LOL!

Have you tried unplugging the EGR valve or removing it sealing it off temp to see if idle went down.

You have made sure that nobody has messed with the idle screw....
Hate to say it, but..........ECM

Phil

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GTDude
OVER 25 years GM experience

I'm wayyyyy ahead of you Phil. I already replaced the EGR valve (wouldn't that throw a code anyways).

The idle screw is fine because the engine ran at 1000 rpms for the first few weeks after I finished the swap. And why would it drop to 800-900 after sitting for a few minutes if it was just set too high.

ALSO I just replaced the ECM with a known good unit from Kick Hill.

I have a used IAC I just put in as well, could be bad but I sure doubt thats it. Two IACs from diff cars both bad. I think its something else.

[This message has been edited by connecticutFIERO (edited 11-25-2002).]

I am no expert but I have a similar problem. Check your thermostat. I was running a 160* thermostat by hypertech and my idle would not drop until I was warmed up; and not at all since winter has started. I changed this out Sunday and put in my stock 195*. The idle dropped considerably. It was still a little high on start up but was not more than 1600 RPM. Of course I run hotter now but it is in normal rang and does not matter in the winter.

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87 GT
Holley Side Scoop---DELETE
K&N Air Filter
Home Page

New Thermo from AutoZone. 195 stock unit. Anyone else got any thoughts?? I sure could ude the help.

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rebuilt 2.8 transplanted into 88 coupe, poly dogbone, poly suspension, rebuilt frnt and rear suspension, customized interior, ported ex manifolds, MSD coil, and more to come.

Theres a vacuum leak somewhere. I also have a EGR block off kit just in case you cracked the new one. They crack extremely E-Z if your not carefull. Gaskets/Lines somethings got a leak/crack somewhere.
Good Luck-
OUT>

quote Originally posted by G-Nasty: Theres a vacuum leak somewhere. I also have a EGR block off kit just in case you cracked the new one. They crack extremely E-Z if your not carefull. Gaskets/Lines somethings got a leak/crack somewhere. Good Luck- OUT>

Thats what I thought, I figured I cracked the new one bangin around on it while putting it in. But I checked with TB cleaner pretty thoroughly and found no leaks.

Did you unplug the battery, to reset the computer. Then drive the beast above 35mgh for 15-30 minutes? Just a thought. I had a formula that had a cracked tube, put the new one on, still high idle. Reset the computer, drobe for 15 minutes, idle went back to normal.

quote Originally posted by RossT: Did you unplug the battery, to reset the computer. Then drive the beast above 35mgh for 15-30 minutes? Just a thought. I had a formula that had a cracked tube, put the new one on, still high idle. Reset the computer, drobe for 15 minutes, idle went back to normal.

Ditto

What about the PCV valve?
If it's stuck open, it creates a vacuum leak.
Just unplug it from the valve cover, and hold your finger over the end. If your idle drops, replace it.
Also, the plastic tube that feeds it connects to a fitting on the bottom of the plenum. Just about impossible to see with everything together, but if it's unplugged, it creates a huge vacuum leak.

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Raydar

I'm not the fig plucker.
I'm the fig plucker's son.
But I'll pluck figs
'Til the fig plucker comes.

Since you mentioned the EGR, I was thinking. Did you install it correctly? You shouldn't have to "bang" it to make it go in correctly. I remember having some trouble reassembling mine the last time. It turns out I was putting part of it in backwards. It could be forced together this way but it would leak. Also make sure that all your vacuum hoses are connected properly. Especially the ones to the throttle body and under the plenum. It's very easy to miss one and this would cause a vacuum leak. If the car idles down to about 800 rpms after it is warm, that should be alright and you might have to live with it that way. You should also make you that the seat for the IAC pintle is clean and not gouged. Finally, you didn't by chance get a bored out throttle body from the Fiero store, did you? I noticed that the butterfly in these has a considerable gap.

The PCV valve is brand new. The IAC is not throwing codes anymore since I replaced it. The TB is not a F store bored out version. The EGR tube is not in backwards, its an 88 on an 87 Y pipe. I checked the EGR tube for cracks after I installed it by spraying TB cleaner just like how I found the crack in the last EGR tube. Its possible a hose got disconnected somewhere by accident but I have yet to find anything.

And to clarify: the engine doesn't idle at 8-900 when warm, it idles at 1500-2000 until I am stopped for at least 2-3 minutes. Then it will drop. I swear I'm about to drive this car off a cliff.

On the brighter side I got new speakers, my horn works now, and I reset the torsion bar on the deck lid so that it now stays up on its own.

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rebuilt 2.8 transplanted into 88 coupe, poly dogbone, poly suspension, rebuilt frnt and rear suspension, customized interior, ported ex manifolds, MSD coil, and more to come.

Hi!
I don't know if my advice will help you but I had the same problem as you..... My EGR Tube was cracked, so I replaced it , BUT , when I took off the Tbody, a rigid hose made of steel fall behind other hoses. The hose I'm speaking about is located behind and under the throttle body it. I reconnect that hose, let the car idle for 10min, and idle was about 900/1000rpm.....
hope this help....
good luck

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Christophe from FRANCE
**1986 PONTIAC FIERO - V6/2,8L**

[This message has been edited by DJWINNI (edited 11-26-2002).]

Have you replaced the throttle position sensor? If yes, did you notice if the old one was adjustable or not? If it was not, is the new one? If it is, that is the problem (I did that very thing on my 4cyl). Took it to Pep Boys and was told that it needs to be adjusted to .54 voolts. Dont know witch two wires you are supposed to hook uo to though, but do know what kind of tool to make so you can do the adjustment your self. If you answered yes to the first 3 questions, let me know and I will explaine hoe to make the tool (it is real simple and very inexpensive). I cannot check my personal e-mail from work (I'm there now). Post herer and I will keep checkin back.

I had a high idle, but not that high, mine was about 1200RPM. We took the ECM apart, and one of them red round things had exploded. I took an ECM out of a 1986 2M4 5-speed (the computer was for a 1985 Auto 4cyl though), the motor is apart now, but I think it cured the problem.

I have pictures of the ECM too somewhere.
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Thanks,
Ben E-Farrer

White 1984 Fiero 2M4, 2.5L Auto
#1192 of 136840

1995 Dodge Ram 1500 ST,
318ci V8, auto, 3.55 open rear,
extended cab, long box 2WD

[This message has been edited by befarrer (edited 11-26-2002).]

I am not positive, but I think the TPS I bought was not adjustable. I did replace it awile ago when I was getting a code for it. Maybe I'll put my old one in again and see if it changes the idle.

quote connecticutFIERO:the engine doesn't idle at 8-900 when warm, it idles at 1500-2000 until I am stopped for at least 2-3 minutes. Then it will drop.

The above leads me to think there could be some binding in the linkage or cable that slow vibrates out.
When the engine is idling high, try moving the throttle arm on the body to a more closed position by hand. If the idle drops, bingo!

Not sure if you tried this. I had EGR troubles but it wasn't the EGR. It was the EGR solenoid. The instructions for testing it in the Factory Service manual are confusing... and I only partially got it right, but I decided to replace it and it cured 100% of my problems. Included:
High idle
sight overheating if driven for 2 hours on highway
drop in gas milage

Best of luck

Its an 87 2.8 with an Isuzu 5 speed in an 88 coupe. Wouldn't the EGR solenoid throw a code? As for the shifting linkage or the Throttle itself, they seem to be fine. The throttle doesn't get stuck in any case. And I have the shifting linkage clamped out of the way so as not to interfere with the throttle. This EGR solenoid theory is looking like the most appealing right now. Maybe I'll try a used one. $100. new!

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rebuilt 2.8 transplanted into 88 coupe, poly dogbone, poly suspension, rebuilt frnt and rear suspension, customized interior, ported ex manifolds, MSD coil, and more to come.

This link might help you with troubleshooting the EGR solenoid. http://www.geocities.com/MotorCity/Garage/5007/fiero_osg/EGR-solenoid.html#clean

being that it will eventually settle down to a regular idle, I would guess the EGR is OK, and there are no vacuum leaks. It might be a low voltage problem. hows the alternator? do your headlight dim when you come to a stop, and brighten when you drive away?

I just tightened the alt belt the other day and I have no problems with power. The only power related problem is my speakers popping and buzzing when the key is in the on position. On side note: the idle does go down to 800-900 after a few minutes at a stop if the engine is warm, but the idle immediately jumops back to 1500-2000 after I start driving again. It idles a constant 1500 in gear.

well, aint this a fun one.....
well, being that it will settle to a "normal" idle, I would say its the ECM wanting the idle higher. now the question is why? TPS? MAP? could close off the EGR and see if that helps. maybe the timing advance keeps jumping the timing up. get a computer diagnostic done, see if theres any sensors reading bad. maybe it is just a sticky throttle cable...

I have replaced every sensor and switch there is to replace including the TPS, new used ECM, and MAP. I guess I could shell out the 100 bucks to have it put on a diagnostics computer, but damn thats a lot of money. **** I have completely built this car with no help other than my dad and now this stupid idle is gonna break me.

This is a long shot but you might want to drop that new thermostat into a pan of water and verify that its opening at 195*. If you want to check it you'll need a cooking thermometer, When the cookng thermo reaches 195 you should see the auto thermostat open and not before.

I was flushing my coolant today and had the thermostat out. It definately causes a high idle.

Dave

[QUOTE]connecticutFIERO: I have the shifting linkage clamped out of the way so as not to interfere with the throttle. /QUOTE]I don't have a manual trans. For those of you who do, what about the above quote? Could that be the cause?

quote Originally posted by 30+mpg: [QUOTE]connecticutFIERO: I have the shifting linkage clamped out of the way so as not to interfere with the throttle. /QUOTE]I don't have a manual trans. For those of you who do, what about the above quote? Could that be the cause?

I don't think so, mainly because it idled fine while I had it clamped before and also because the shifting cables have no bearing over idle.

quote Originally posted by connecticutFIERO: On side note: the idle does go down to 800-900 after a few minutes at a stop if the engine is warm, but the idle immediately jumops back to 1500-2000 after I start driving again. It idles a constant 1500 in gear.

I had another fiero that DID THE SAME EXACT THING.
You would come to a stop sign(engine warm), and the idle would be up around 1500, If you were stopped long enough, the idle would eventually drop to the propper level. It would just take forever. But the idle should drop down as soon as the car was out of gear. Sometimes it would take so long for the idle to come down, that it would throw the code for IAC (enven though it was new). I tried everything. I switched sensors with my 1200 mile 88gt, no luck. I even changed the ECM coolant sensor, still no luck, It was almost like the car wasen't switching from closed loop to open loop. The only thing I did not check was the timing, cuz I sold the car before I got around to it. Dang thing was driving me nuts.

I did notice that the cap to idle srew on top of the TB was off, so I can only assume that the previous owner was messing with the idle screw. I eventually bought a scanner to see if I could check for open/closed loop, but I sold the car before I could hook it up.

I feel your pain!!

I just got some great advice from a guy not registered here but who sent me an email. He mentioned how the coolant temp sending unit or switch located under the Distributor could cause the high idle because it is what tells the ECM when the car is warm enough to kick the idle down. The thing is already bought this sending unit and was in the process of installing when I noticed the wire connector was completely deteriorated and falling apart. So I was waiting till I could scrape up the $15 for a new one and replace both at my leisure. Seems I should hurry up and try this before I do anything else. It seems like this could be my problem. My temp gauge is all screwy as well, so I'm betting on this unit to fix the idle (crosses fingers).

On A side note: looks like I probably have a good extra EGR tube now that I replaced it when it wasn't the high idle culprit.

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rebuilt 2.8 transplanted into 88 coupe, poly dogbone, poly suspension, rebuilt frnt and rear suspension, customized interior, ported ex manifolds, MSD coil, and more to come.

there are 2 temp sending units - one for the guage, one for the ECM. the one by the dist. is the sender for the guage. the one for the ECM is on the intake manifold, above the pulleys. it sticks out horizontaly (towards passnegr wheelwell).

Hey Pyrinth I beleive the one by the thermostat housing is the sensor which relays info to the switch which send the info to both the ECM and the gauge, but I am certainly not positive about that.

Do you know what the other sensor next to the coolant sensor is by the Thermo housing? I noticed it the other day and realised that I had one more sensor to replace. Is it the cold start switch?

The ecm coolant sender is directly above the waterpump, below the thermostat housing. This sender only sends message to the ecm (not the guage). Gm has an updated part# for this sender and it only runs about $8 at the dealer. I replaced this, and it did not help my problem.

So are you saying that the coolant temp sender below the distributor's sole function is sending a signal to the gauge? Why not just use the the coolant temp sensor for that to save on costs? I think there is more than meets the eye here. (in computerized voice) Robots in disguise.

no really - its true. 2 temp sensors. and the two switches on top of the intake manifold, near the thermostat housing are the fan switch & cold start injector switch. yes, not a well thought out scheme....

Dan, i finally got on the forum using rufus@paintballing.us and ID: jaxmancan- - -
check your e-mail at @harthosp as i sent a rather longwinded story.....Marty

I'm interested now, the sendor for the guage only sends signal to the gauge and not the ecm right?

Yes!