need help w/ stalling

[redross006]

Hi, I hope someone can help. I have a 1993 lumina z34and whenever islow down or stop at a light the engine dies.It also dies if it idles in park for more than 5 minutes. The CEL is not coming on but it does work. Ive hadit tested and it's not showing any codes. It also has a very rich smelling exhaust. This is what I have replaced. New plugs and wires, new catalytic converter, new o2 sensor, new pvc valve, new fuel filter ,air filter, new vacuum lines, and a new egr valve. I let it run out of gas and thought it could be eithera bad fuel pump or maybe some cloggedinjectors. But was told if the pump was bad that the car would have died by now. (it's been 4 months since it ran out of gas). And I've tried injector cleaner but to no avail. When the engine stalls it is becaue the RPM's are dropping to around 500.

[richtazz]

there is an electric stepper motor in the throttle body called the IAC (Idle Air Control) valve. It opens and closes at idle/part throttle, to keep the air fuel mixture correct. They can get carboned up preventing them from doing their job, and the symptoms you describe are textbook IAC valve. You can remove the IAC and clean the cone shaped pintle, as well as the bore in the throttle body where it mounts with carb cleaner and see if it helps. Be careful not to move the IAC pintle in and out while cleaning it, or you'll mess up it's calibration.

[tblake]

Ha, yeah, and dont go overboard with the carb cleaner. I had my car in the shop to put in a new thermostat. I took the throttle body off, and thought while I was there would clean it up with my carb cleaner. I had left the IAC and TPS on it, and soaked it down and cleaned it up. Upon installing everything, (and a new throttle body gasket), the car started MINT, and died. I attributed the first stall to IAC out of calibration or something. Started again, MINT, died. Started, died, started died, started, kept her running with foot on gas, and slowly let off to try to recalibrate the IAC. The car Died again. Getting frustrated, I grabbed a TECH 2, and commanded idle at 1000 rpm, started it, and it died. so i took the iac out, and commanded idle haigh and low, watching the pintle. It would move out, but not back in, it only could be felt clicking. I ordered a new IAC, put it in, and the car ran Beautiful. Either he IAC motor took that exact second to tak a shit on me when i had my car in the nice warm shop, (less likely), or I fucked it up using carb cleaner. Possably used too much, leaked inside, and melted the coating off of the finly wrapped wire shorting it all out. (more ikely). After it was replaced i did move it in and out with my fingers, and it mover freely. So it was shot.

[redross006]

Well I did what you said but to no avail. I removed the IAC and cleaned it with some intake cleaner and for good measure sprayed the iside of the throttle body to. Also after reading other threads I thought it might be the TCC so I unhooked the wire on the tranny like some said and this only made the car run worse, like I had to give it alot of gas just to get the car to run at low speed, so I hooked it back up. I hope someone can help me. I really like the look of the car, and this is my only mode of transportation. Plus I can't afford a good mechanic or another car. Thanx for all help and thanx in advance for any added replies.

[mjtr21]

i am having the same exact problems as he is. where exactly is the IAC valve? this sounds like my problem because when ever i come to a stop my RPM's fluctuate between 500 and 1000. thanks.

[tator41143]

I had similar problem with my Lumina.It would die at red lights.Do you smell gas fumes around the engine.If you do,pull vacuum lines,carefully, from throttle body and check to see if fuel is running back out of fuel regulator vacuum line.(check the line for vacuum leak,also)Also,check ign. module and coils for intermittent problems.You can have them checked at Autozone.