I have a 92 740 B230F (rex/regina) that really has a bad idle, but only when the outdoor temperature is cold (~40F and below in Wisconsin). I first noticed this problem last winter/spring, but it went away over the summer, and now it is back. The TB, TPS, IAC, filters, etc are all up to spec.

Here are some of the symptoms:

The engine starts just fine but then really gets to shaking for a few minutes until the dash temperature gauge just starts to move away from cold. During this time the engine will idle around 1000 rpm but will drop to 300 rpm and almost stall out if I shift from Park into gear. Also, the engine will absolutely stall if I try and put any throttle to it.

However, once the engine warms up everything is fine. I've been doing some research on this problem and the fact that this issue is so seasonally dependent has me leaning toward suspecting the ECT sensor. However, I do have a small vacuum leak behind the cabin temperature controller in the dash, but would a vacuum leak only cause problems in cold weather?

The ECT doesn't cost much ($35 at FCP) but I wanted to get some expert advice before I start buying parts.

Thanks in advance,

JTK

 

I would pull codes before you spend money. It could be several things.

Regards, Andrew.