When im setting at a stop light or a stop sign, the idle will drop to 400rpm and then jump to the normal idle. Anybody have problem, and if so how did u fix it.

 

A few common fixes that are worth doing anyways are, clean the throttle body, run some seafoam through the brake booster line, and make sure your battery is in good condition, have clean tight connections and add an additional ground wire from your negative terminal to the alternator bracket. One of those things should fix your random idle issues.

 

I agree, check the throttle body first as well as the air filter.

 

One guy swore that changing his gas cap to a locking one fixed his weird idle issue.

 

Agree. Try these things first and see if they fix it. Many times it is something simple

 

My wife's JKU had the same issue turned out to be a bad plug wire.

 

Cool thanks for the info

 

Been having this same problem too. Happens randomly. Been to the dealership 3x and they cant fix it because "nothing is wrong". I had the throttle body cleaned and it still happened two days later. Guess I'll have to check the plug wires but if anyone has more info I'd like to know too!

 

It could be the PCV. It can get stuck open.

 

I have the same problem. It only occurs if I start it and leave it in park for a little bit. Never yet at a red light.