high idle and then it stalls?

[sholoveyou]

i have a 94 mtx and i was wondering if anyone knows why my car is stalling? it only does it some times when im stoped at a light it idles around 2000 and then the rpms drop and it wants to stall. if i tap the gas it stays running just fine. does anyone know what this could be thanks for the help.

 

[Devin]

2000 is too high. Check your IAC and your MAF.

 

[St Louis SHO]

almost sounds like the big vacuum line fell off the rear of the intake.

 

[SHO GoDz 89]

I've had the same problem with another car I owned. It turned out to be the EGR valve. When the EGR valve sticks open like that, it results in a rough idle and sometimes stalling. My 1985 Daytona had a very high idle because of this, it would rev up to 4k or sometimes 5k (very bad for an old motor) and I'd have to shut the car off a few times just to have it come back to normal.

 

[LiLGhettoSmurf]

I don't believe the MTX's had an EGR system. Sounds like a vacuum line I had something similar happen to me, but mine idled really low and stalled out, but if I gave it gas it would stay alive.

 

[93rev2sev]

I would check for a vacuum leak as suggested. I would also make darn sure the IAC was operating correctly.

IAC for anyone not familiar is the Idle Air Control. It's on the intake manifold, bolted to the backside of the throttle body mount. It's a valve that controls the amount of air the engine gets when the throttle blade is closed. If it's sticking, the car will idle for crap. The PCV system allows crankcase air into the intake...and the IAC. Eventually, the IAC gets gooped up with dirty oil and starts to stick.

 

[sholoveyou]

I would check for a vacuum leak as suggested. I would also make darn sure the IAC was operating correctly.

IAC for anyone not familiar is the Idle Air Control. It's on the intake manifold, bolted to the backside of the throttle body mount. It's a valve that controls the amount of air the engine gets when the throttle blade is closed. If it's sticking, the car will idle for crap. The PCV system allows crankcase air into the intake...and the IAC. Eventually, the IAC gets gooped up with dirty oil and starts to stick.

how do i check to make sure it is working properly? it only does this sometimes and it idles at 2000 then it drops thats why i dont think it is a vacuum leak.

 

[93rev2sev]

I havent searched for the procedure, but it's here somewhere...