my 98 zj has an issue during idle where it will idle up and down.....between approx. 600rpms to about 1200 or so(maybe 1100). recent dist cap, rotor, plugs, and wire change. airfilter looks good as well so im thinking its a fuel problem.....either fuel pump/filter, idle air control valve, or even injectors. wanted to know if this is a common issue and if anyone else has had a similar problem and what it was.

 

not sure if it matters but just incase it has a 4.0l motor with167xxx miles on it.

 

Could be idle air control or throttle position sensors.

 

Bad coolant temp sensor will do this also

 

Is there anyway to check to see if one of those is bad without taking it in? I doesnt always do it. I need to pay more attention to when I does. I know it does it more after you first start it.....I also believe when its cold out it gets worse

 

My 97 ZJ was doing this over the summer. I tossed a new TPS in it and it fixed the issue. Here's a link to the 4.0 ones that we carry if that's even the issue.

Jeep Grand Cherokee Throttle Position Sensor