Weird Idling Problem

brtnstrns

Member
Dec 19, 2003
606
11
19
Lewisville, TX
I've been having this issue for a while. Since the time I bought the car a few months ago, it revs down real slowly which I've been told over and over again is how the engine is supposed to be. Well as soon as this cold weather came into Texas, I've been having a problem where when I start the car up, until the engine has warmed up, the revs will drop very suddenly when I depress the clutch and the car will stall itself out. MOST of the time, after the car has warmed up it will figure itself out and the engine will rev down slowly like its supposed to and no longer stall out. For about a week though, the car would not get over the problem even when the motor warmed up. After a couple days of this the "Service Engine Soon" light came on. Once the weather got back up to about 70 degrees the car started right up with no problems and the service engine light went off. Now a cold front has moved in and the car is messing up again doing the same thing, revving down quickly and stalling out. Currently, it will sort itself out once its warmed up. I've run injector cleaner in my tank and seafoamed the engine today. I have throttlebody cleaner and plan to disassemble the throttle body, IAF, etc and clean it up in hopes that there is a problem in the intake system. Can anyone come up with any other ideas as to what might be happening? It seems to correlate a lot with the weather.
 
Yes. Your Idle Air Controller (IAC) is most likely bad. The IAC with the black vent can not be cleaned. Replace it.

Autozone makes a lower cost IAC. I have had good results with.

If you wish to diagnose the problem, there are many threads on how to do it.

Regarding the DTC, please post the code.
 
I tried checking the code with a friends code reader but it said that there were no codes. Now the lights off so I don't think I can try to check it elsewhere.

The IAC at autozone is only $50 so I'll try that one out seeing that the mustang sites have them for $125.