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High idle, smells like gas, running out of things to replace


NAXJA Forum User

I've been having one hell of a time tracking down an issue that's preventing my Jeep from running below 1100rpm. The jeep in question is a 1995 Automatic XJ with the 4.0L.

Main issue is how high the idle is. It also has a ton of vibrations, feels almost jerky in gear without my foot on the pedal, and consumes a shit ton of gas. Like 100 miles per tank. The idle won't go down below 1100rpm when warm, or in gear or with the AC on. It does gradually come down from about 2000rpm when cold. I overheated the hell out of the thing a month ago due to my mechanical fan failing while I was in traffic, but I hope it was unrelated.

Here's what I have already replaced:
Plugs, wires, rotor, cap, and coil.
Replaced the plugs again after the truck overheated.
The IAC and TPS.
Coolant temp sensor and thermostat.
Motor mounts were replaced with Rusty's rubber mounts (that wasn't fun)
Catalytic converter

Here's what I've done:
Cleaned the throttle body.
Checked all vacuum fittings and replaced cracked ones.
Sprayed the manifold with starter fluid for vacuum leaks.
Checked grounding voltage.
Checked fuel pressure (33psi at idle)
Checked manifold pressure (17in Hg at idle, but not a steady needle)

My experience and my research is telling me that I have a massive vacuum leak wasting air somewhere, but I also feel like the timing is off due to the unsteady needle. What could be causing my idle to be that high at all times? It's driving me crazy.

Thank you for all your help!
The only time I've experienced a high idle like that was when I had a major vacuum leak from the power brake booster. This was a long time ago but if I remember correctly I was not able to detect it by spraying starter fluid around in the engine bay and I remember it took me a long time to finally figure it out.
I had a mechanic friend come out to take a look. Turns out my head gasket blew on cylinder one and it was just launching unburned gas down the pipe. Fun stuff.

Thank you for your help!