bigjon3769

Hello everyone,

I need some help chasing down my problem. I have a 2004 Grand Cherokee 4.0.

My problem is, when the engine warms up to operating temps, the idle gets fairly low (600-650 RPM). When I put it in to drive or reverse, the idle speed drops again (500-550 RPM). This causes things to rattle a bit and it feels like it's about to stall. The car has stalled in the past at red lights, but not since I've put a bit of work in to her. The car has a constant tremor at idle, but it goes away while driving. I though maybe it might be low compression, but the problem doesn't follow the RPM.

So far, I've replaced:

TPS
IAC
Downstream O2 sensor bank 2 (CEL from corroded wires touching the exhaust pipe)
PCV elbows and grommets
Any hose that was brittle when removing them
Valve cover gasket
Head gasket
Spark plugs

I've also cleaned the throttle body twice for good measure and that gasket has been replaced.

My first thought was there might be a vacuum leak somewhere, so I did the 'ol propane torch (not lit of course) across all vacuum lines and still nothing. I thought maybe the propane wasn't good enough, so I switched to starter fluid across the lines. Still nothing. I am not getting any CEL, so I'm chasing a ghost at this point.

Any help from this point would be greatly appreciated!