well i got this really high idle, its 2500 in park and like 1500 in drive

it started last year and it would be high one day or week and be normal the next day for no apparent reason.
then like 5 months ago, it stayed high (like 2500 in park) but sometimes it would drop down to like 500 even on startup and i would have to push on the gas or it would die till it warmed up.
and since then, its been at 2500 in park and i would really like to solve this problem, as its a pain to drive and its eating up gas!

i changed the IAC valve, didn't do anything
i can take the IAC valve out and adjust it by hand, then not plug it in and make the idle what ever i want it to be, but i thats just bypassing the problem.


here is a little video that might help someone help me!!

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(it does that by itself, i did not push on the gas at all)
if that does not pop up for some reason?? here is the link
http://www.youtube.com/watch?v=D9F92Tfzn6k

its a '89 firebird v6 2.8

anyone have a similar problem or know what could be the problem?
it could be a vacuum leak, but i have not found one, where should i look?

any help is appreciated, thanks

 

you probably have old cracked vaccum line replace them all one at a time I had the same problem on my 85 camaro

 

For Vaccuum leaks try spraying staring fluid on your lines. Both the rubber and the plastic ones. It will rev if you hit a leak. It could be quite a few things. Any codes?

 

mine did that when my mass air flow sensor went out. could also be vacuum lines tho. id def check and replace lines first cuz that sensor will cost you a good bit of change

 

Could also be the idle air control valve under the throttle body. try removing the valve and plugging the hole with your finger. If it idles lower and stalls, then its the valve not sealing properly. Sometimes its just carbon build-up, sometimes its a bad valve.

 

got any engine codes? 33 or 34 replace your mass air flow sensor. my cars got that problem right now, cept not as high of an idle. ive got the idiot light though.

also, check your spark plugs/spark plug wires. my car was doing EXACTLY what yours is at one point about a month after i got it. i put new plugs in as soon as i bought it, so it took me a day or so to realize it could be the plugs or the wires. when i pulled one of the wires, the metal inside stayed on the plug. i had a bad wire somehow (on brand new performance wires too). i replaced them with the generic advance auto wires and theyve been great.

 

there is another idle air control valve? i replaced one, and it did nothing



ok, thanks, I'll check that sometime soon, and idk if there is any codes, but the engine light does not come on



anyone think it could be the throttle body sensor (aka TP sensor or TPS)?

 

TPS sensor doesn't control idle, all parameters are coarse tuned by RPM/Map (or MAF). Then fine tuned with TPS, IAT, O2 sensor, etc. Pull the IAC out, and plug it in. Turn the car on and see if it moves at all (don't start the engine, just put it to ACC). If it does not move at all, then that's your problem. I had the exact same problem you had, and I couldn't figure it out, until I tested the IAC, and found that was the problem. Replaced it, and fixed 90% of the driveability issues I had with my firebird. IAC = idle air control unit.

 

You are MOSTLY right. No, the TPS doesn't control the idle speed directly. However, if it is sending the wrong signal to the ECM, the idle IS affected. The ECM is looking for a signal from the TPS of about .55 VDC at idle. If the TPS is not set correctly (even at the full extent of its adjustment on 88+ models), the ECM will think the throttle is open even if the plate is closed, and adjust fuel and the IAC to compensate. This guy, with this problem, should be getting a code 25 (ECM unable to set idle speed within parameters) if he is getting ANY code, unless he has other problems as well.
You're also forgetting that he has to turn the ignition on and then off again to see the IAC move if it is going to. Just don't forget to point the pintle into a rag or something because the pintle WILL shoot out of the IAC, under spring pressure, if the motor is working correctly, due to the ECM trying to "home" the pintle against the bore in the TB.

 

first post
but thanks for the info

i tested the IAC and it moves and it shot out, so i think it works

so i should be able to use a volt meter on the tps to see if it is working properly or not?

 

Between the blue signal wire and the ground wire, yes. If the TPS is out of spec, you will need to remove it and elongate the holes.
I had been having idle control problems for 5 years until I did both, replacing the IAC 3 times, the IAC wiring twice, and my TPS (switched from old upper plenum to 3.1 plenum and needed a different system so I had to adapt things over). When I plugged in the TPS, it was sending a signal of .77 VDC to the ECM and I wasn't enjoying my gas mileage any. I also had a code 44, and that is the reason for my crappy low hot idle speed, but my injectors are screwy, so don't worry about that.

:edit: Also, are you getting any codes? I was wrong, it's a code 35 for idle speed control problems.

 

ok, so its at like .5VDC at idle and 4VDC at wide open throttle
i don't know about any codes poping up, is there an easy and cheap way to get those? but no "service engine soon" light comes on

 

Pull the black cover off of the driver's side hush panel under the right side of the steering wheel, facing you as you sit in the seat. Put a paper clip into the 2 holes of the 12-pin connector that are in the top right corner. Meaning, put the clip into the one IN the corner and the one to its left. Turn the key on but don't start the engine. The SES light will flash once, pause, then once again followed by a pause and 2 flashes 3 times before any other codes are flashed. The number of flashes tells the number of the code. For instance, 3 flashes followed by a pause and then five flashes is code 35. There is a longer pause between flash sets to separate the codes. And don't worry if the radiator fan comes on when you jump the terminals in the diagnostic connector. It's designed to do that.

 

I wasn't aware if you had tested the new IAC before it was replaced, and I've received broken parts before, that was why I suggested it, my appologies.

You are correct, however I do believe the IAC will shudder, and move when you first turn the ignition on. This is why, no matter what temp it is outside, the car will idle at 1200-1300rpm for at least a split second. He shouldn't have to turn the ignition back off to see this, but then again I'm not completely sure if the V6 versions are vastly different, I'm only applying my knowledge from speed density V8 electronics (thought I do believe the idle circuits would be similar).

If you find it's not a TPS issue, I would go back to searching out vacuum leaks like a lot of other people have suggested. Perhaps not just line leaks, but gasket leaks, etc. A scan tool, or laptop based program would help with this a lot.

 

thanks, and it only blinked x xx so thats 12, right? so it has no codes?

hopefully this weekend, i will be able to replace the throttle body gasket and replace some vacuum lines, but if thats not the problem, I'll come back here!
you guys are really a lot of help

 

well it got sunny out for a while and it was normal for a couple weeks, and well now its high again since it started raining

so i am convinced some sensor or something is getting wet/moisture in it which is making it malfunction.

anyone know any sensor that could do that? what should i replace first?
thanks

 

Mine idled high and i discovered a vaccuum hose completely off going to a cannister on the drivers side front by the radiator. I am sure you probably checked there but just a suggestion.

 

haha, i actually found that.... by accident, i went to put my gfx back on and i saw it!... but i plugged that in and nothing happened, soon as i get this damn paint job finished ima replace alot of those vacuum lines, i hope that fixes it....