Once engine is hot,( been running at high speed at least 30 min) and only then, the car stalls out in stop and go traffic. Mechanic says "may be costly idle controller" but not sure. Anyone know of anything else it could be? How likely is it to be a temperature control sensor problem? Any info appreciated.

Once engine is hot,( been running at high speed at least 30 min) and only then, the car stalls out in stop and go traffic. Mechanic says "may be costly idle controller" but not sure. Anyone know of anything else it could be? How likely is it to be a temperature control sensor problem? Any info appreciated.

If you can start the car right after the stall, it could be a dirty EGR valve. A good cleaning should do it.

If the engine is cranking but not starting right after the stall, it coud be your temp sensor. This one is very erratic but a dealer could detect it with the computer since the temp sensor reading goes craizy when defective and that normally results in sending more gas to the engine causing an enriched stalling.

If your rpms go up to 1000-1500 on a cold start and then to 750-800 when car is warmed up your air intake control valve is OK.

good luck

Thanks for your input. I will let you know how it gets resolved.