irratic stalling

[shelby987]

I have a 1994 SHO MTX that was just purchased about 2 months ago. The car was purchased with a bad thermostat that has since been fixed. The car would stall first thing in the cold michigan winter mornings if not given a lot of gas at launch, but i figured it was due to the thermostat. That has since been fixed, and now the car seems to have a real problem with maintaining idle, a couple of times i have been sitting at a light, with the car in neutral, and the idle will drop from 1,000rpm to stall......when i start it back up it will start to run at 1,500 rpm.

The MAF has been cleaned, the thermostat is good, I have also noticed that during highway driving with super in the tank the car only averages about 22mpg (normal 70mph cruise control driving).

Any help would be appreciated, its getting pretty old having to fire the car up at a stop light every time i come to a stop.

p.s. the car only has 66k miles on it.
Thanks

 

[uSHOslow]

This almost sounds like it could be an oxygen sensor problem, however I'm sure someone with more knowledge will chime in.

 

[shelby987]

I am new to this car, so you will have to forgive me, can anyone confirm that this is the problem (can i trace the codes to make sure thats it, or will it not show up?).

Also, does this car have an O2 sensor on each bank, or is there only one in the junction of the y-pipe?

I heard mention of a bad IAB possibly causing this problem (or one like it). Any help in narrowing down the hunt would be appreciated, also a ball park figure of the cost would be great too (just parts, i do all my own labor).

Thanks

 

[shoteen95]

there are two O2 sensors..one for each bank...if your CEL is coming on it would be wise to check your codes. its pretty simple to do..takes less than 10 minutes..the idle and stalling problems sound like they're related to the idle air bypass. It's the thing on the intake..just left of the throttle body.. it controls the amount of air that goes into the engine at idle (when the throttle body plate is closed)..sometimes it gets fouled up and so will your idle. You can remove it and clean it out..might solve your idle problem.

 

[kurtis adum]

i second the iab vavle. Thats where i would start.
kurt

 

[shelby987]

can someone give me an idea of what i am looking for, what does the IAB look like, is it above or below the intake? Should I just clean it out with carb and choke cleaner like the MAF?
Thanks

 

[SHOZ123]

The IAB (Idle Air Bypass), properly called the IAC (Idle Air Control) on anything from '93 on, is the cylinder shaped item with the electrical plug behind the throttle body. It's sole purpose is to control the air flow past the throttle plate to control/maintain idle and control/limit engine braking.

Neither the thermostat or O2 sensors will have any affect on idle when the engine is dead cold.

 

[heath_06p]

i had the same problem and it ended up being my fuel filter. check that