Jeep 4.0 idle issue.

TapouT

Well-Known Member
Joined
Oct 5, 2008
Location
Hickory nc
I've got a 1998 Jeep Grand Cherokee with a 4.0...I noticed Saturday while at The Flats that it was having an idle issue after warm starting it while wheeling. Say I was parked for 1-10 minutes and went back into the Jeep and started it, the Jeep would idle very rough. It didn't do it every single time I started it but it did it quite often. It sounded like it was under water to be honest. One kick of the throttle and it would clear itself out and it wouldn't hesitate when I gave it gas either. If I let it sit there and run while idling like that it would eventually clear itself out after 20-30 seconds.

It's an intermittent issue. It doesn't always do it but revving it up will clear it out every time it begins to idle like that and then it will go back to idling like normal although it always has had a sort of rough idle. The Jeep has new Champion plugs gapped at 0.035", new spark plug wires, new distributor cap & rotor button, new TPS, new IACV. It does NOT have a check engine light or stored codes. A friend of mine said that it could possibly be an injector bleeding fuel whenever the Jeep is not running and that's causing it to act like it's flooded somewhat?! I just figured I would ask a more experienced group before I start throwing parts at it. Thanks for the help guys!
 
Are you losing any water/coolant? Could possibly be a blown head gasket. Causing water to leak into the cylinders when the engine is off. But in theory its would do it while running and idling as well, but not always.
 
My 92 xj does that at a hot day at URE or wheeling when you can't get the heat out from under the hood that well. People have fixed it with hood vents or by shielding the intake area. I believe the problem is often referred to as heat soak in the injectors. It has happened to me for four years now but has never gotten bad to a point I can't start the engine again. If it gets worse try hood vents or shielding like mentioned.
 
mine did somewhat similarly until it started dying randomly.. coil had started breaking down internally, bubbled up the encapsulation slightly where it was arcing.
 
I had an XJ that would get heat soak pretty bad. The fuel I bought had a lot to do with it. It did it a lot with shell or Bp,but hardly ever with Hess.
 
Every XJ I've had I have wheeled with the hood popped during the summer months. It helps cool it a lot, but 9 out of 10 people I'd pass would say "hey brah! Your hoods open brah!"

Most annoying thing ever. Got hood vents on the newest one, but it don't run so idk how well they work yet.
 
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