Jeep: low rpms and rough idle, jeep cherokee laredo, throttle position sensor

Question
Hello! The expert can't answer your question.

Your Question was:

When my jeep warms up and in drive when I stop at a light the rpm's drop to 4000 rpm's and at times idles rough or will surge. I took it to the dealer they replaced the I

AC motor but otherwise found nothing wrong.

Following is the reason:

I need more info. Year, model, engine

Expert: Ryan

It is a 2000 Jeep Cherokee Laredo V8 AWD

Answer
Well the first issue....sitting at a stop light, you rpm should be way below 4000. At idle, it should be around 900 rpm. If that was a spelling mistake and you meant 400 rpm, then I understand.

This is a hard problem to solve. Especially if the dealer cannot find anything wrong. About the only way to really find the problem, is to start with basics, like a tune up (plug, wires, air filter, etc)

If none of that fixes your the rough idle you will have to move on to the sensors.

You will probably want to pick up a Haynes or Chiltons manual. You will want to check your throttle position sensor, Idle air control, and map sensor. You will also want to check your fuel pressure.