View Full Version : 87 XJ 4.0 Bad Idle and Stalling

04-08-2008, 02:46 PM
So my XJ is runnin weird. 87 XJ Renix 4.0/Auto. When ya fire it up it runs fine for a couple minutes, then the idle bounces around, between 100 and 800. When it idles really low like that, sounds like I have a wild cam in it. Kinda like the timing is off, or it's missing.

When I'm driving it, and pull up to a stop sign or to make a turn, if I don't put it in Neutral and keep my foot on the gas, it will stall. Other than that it runs fine above 1000 rpm, acceleration seems unaffected. Any ideas what the hell is goin on?

I cleaned and replaced the IAC, TPS and checked the plugs. No change :confused:

I have a complete 89 XJ 4.0 to take parts from if I need them.

04-09-2008, 10:23 AM
i bought a mj for 50 bucks for postill last year did the same thing didnt look too hard at it as i got it a few days before sold it to a freind after and it blew a clyinder couple days after:dontknow: might have somthin to do with timing i would check the timin for sure good luck man [cheers]

04-09-2008, 10:51 AM
Timing is fine, as it is not adjustable on the engines.

04-09-2008, 01:29 PM
O2 sensor would be my first suspect

04-09-2008, 05:42 PM
I changed the O2 sensor and nothin. Figured out it was a vacuum line to the EGR. Works good now.

04-10-2008, 10:06 AM
good to know glad to hear you got it figured out