bad_idea

This blasted jeep. I've had my 1990 XJ for about 8 or 9 years now. I have completed most all of cruiser's tips through the years of owning it. Recently it has started idling high intermittently. Sometimes when I start it, it will idle between 1800-2200. When it does, I can rev it a couple times after a minute or so and the idle will drop back down. Other times revving it doesn't resolve the issue, but if I turn it off and back on again then it will idle right. No real rhyme or reason to it. I replaced the IAC today with no change. The port for the IAC is squeaky clean. I replaced the intake manifold gasket about 6 months ago because it was leaking pretty bad. The TPS was replaced when I got the jeep. I verified adjustment of the TPS a few months ago. Any ideas?

dmoe69

I'd go back and check the sensor ground. Best way to do this is by back probing the "B" terminal of the TPS connector and putting the other probe of the multimeter on the negative terminal of the battery. Cruiser's tip 8 has the procedure for this at the top of the page, you're looking for <1 Ohm. When I had intermittent high idle, I was surprised to find that the dipstick ground had degraded in less than 2 year's time. Also, since you mentioned that you replaced the intake manifold gasket, it would be a good idea to check the manifold fasteners to ensure they are still wrench tight.

bad_idea

I’ve been putting off checking the manifold bolts. I know I need to, but it’s a nuisance.

I checked that ground at the dipstick tube and found the wires in poor shape. I cut the first three inches off of the wires and spliced in new wire. Grounds are good now. That didn’t change how it ran. Fired it up and it revved to 2200 RPMs.

That irritated me so I started unplugging things to see if it would change the idle. I unplugged that flat connector with three wires going to the TPS and the idle dropped down and it idled nice. I plugged and unplugged it a couple times and it’s been running fine since.

I’m at Uwharrie national forest now. We’ll be here for the weekend. I’ll report back if it idles up again.