I had erratic idle (high and surging)on my 95 dakota 3.9 when engine is warm/hot. Replaced coolant temp sensor. Started let it run to normal temp no problem. Later tried to start wouldn't start. Ringing sound coming from ecm. Disconnected battery, pulled and reconnected tps reconnected battery started and ran fine. Not sure if the tps or ecm is bad. how can I narrow it down? Appreciate any help.

 

What year and engine of truck do you have? On 92-96 there are 2 coolant temp sensors. Are you sure you changed the correct one? The TPS is not to expensive buy one and see. The ECM will be $200-300. If you can find a used ECM at a junkyard try it.

 

It's a 95 witha 3.9 changed both sensors. Thanks

 

The surging, erratic idle problem sounds like your IAC. It's on the back of the intake manifold. Pull it and clean it up. Also clean where it seats up inside. I used a mirror and flashlight to see in there.

I also disconnect my battery before messing with sensors, or anything electrical. You can re-set your computer by removing the neg. battery cable, and turning your key to the on position and leave it there for 20- 30 seconds. Not positive if you have to do the key, but I always do.