I've read a number of threads about rough idling, but none seem to address my problem. The car idles okay when cold, but when its hot it gets really choppy, the rpms drop and it feels like it wants to stall. Otherwise, it runs well and the idle gets better when the AC comes on or I step on the gas enough to get the revs to 1000rpm. Any ideas?

GRRR Year Model Mileage engine and tranny

check your idle air control motor or your mass air sensor. (is there a run on these things?). the car is fine because it is in open loop when cold. Its running off pre determined values. When the car warms up, it goes into closed loop, which is when its reading all the sensors. the IAC is a slave, meaning it takes commands from the ecu. the Air Sensor gives the ecu data to make decisons. Another possability is a bad vaccum line. (electronics not my strong point without knowing codes, im good at multiple codes)

We really need to know the other info before we start telling you ideas.

 

nipper

Thanks for the reply. When I first checked for codes ther were none- now there are. The intake manifold has failed on cylinders one and two. I guess it was a progressive deterioration. A spray of starting fluid confirms the problem. I'm not sure why it failed since its been replaced relatively recently. Oh well! Maybe its the nitrous (just kidding!).