My 88 starts great but even before it warms up it seems to idle up and down. It will bog down slighltly then idle up high then even out then bog down then idle up...etc.. sound familiar to anyone? It runs smooth once I start going and only does this at idle. Its not the fan kicking on and off either.. Thanks

 

Maybe the TPS?

 

IAC clogged or dirty maybe?

 

My jeep was acting very similar to that and after a few months it even started backfiring through the intake manifold. I replaced the TPS, the MAP, running seafoam, cleaned the Idle Air Control and all those fixed nothing. What it ended up being was the upstream 02 sensor. Popped it in and it ran like a champ. Mine is a 97 so I can't gaurantee thats what it is cause you have a RENIX I believe but thats what my problem was. Just thought I'd throw it out there for ya.

 

thanks for all the tips guys.. so far I have ran seafoam but I will check those other things out.. how do i go about checking the TPS?

 

and the IAC.. is it in the intake? sorry I am new to jeeping...

 

The IAC should be right there hooked into the throttle body. At least thats where mines at. On mine if your looking at the throttle body from the front of the jeep its on the left side. Grab some mass air flow sensor cleaner from autozone and spray it. You can wipe it lightly but make sure you don't twist or turn the cylindrical part of it. That can screw it up. I'd give your TPS and MAP a spray too since your in there already. I believe on your year you can adjust your TPS but I don't know how for sure. My TPS is auto adjusted by the ecm. After cleaning all those if you don't notice any type of improvement whatsoever then it might be your o2 in your downpipe.