Idle surging

[Chrisman889]

I have a 93 xlt, recently the engine has been surging to a higher rpm when I'm stopped at a light. Whether in P or D it still surges up and down, which it used to do when the air filter was dirty. I just recently cleaned the MAF and I regularly clean the IAC, has a fairly new PCV. Hopefully it's not one of the intake manifold gaskets. It does idle sort of rough in general.

 

[awood]

Throttle body dirty, or vacuum leak?? Maybe try following all the vacuum hoses from the tree on the intake all the way to the end of each line (except maybe the one going down to the tranny modulator). There's a hidden line under the upper plenum aft of the throttle body.

Any codes?

 

[Chrisman889]

No codes. It's not a constant surge. It will sit normal for a while and then it sounds like something clicks on and the idle raises to a little above 1000. I recently changed the tranny vacuum module and I'm pretty sure the line was good but I will check the other lines.