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cswetnam 06-19-2008 10:59 AM

Random engine stall at low/high speeds and random missfire
After reading a lot of posts on here, not sure if I found one w/ my exact "bundle of issues." If so, point me in the direction.

99 xj, 4.0L, 190k miles.

Symptoms: In park - slightly rough idle but it maintains the 900rpm with a little wavering back and forth(approx. 20rpm). In drive @ a stop - slightly rough idle with strong, random lope in the idle. Sometimes when this lope occurs, engine will stall. Sometimes not. Engine always starts right back up.

Engine will randomly stall when decelerating @ any speed. 70 mph and let off the gas, engine stalls. Coming to a stop, engine stalls. This will happen 3-4 times a week, completely random. Engine always starts back up.

I think I've got a stalling issue and a missfire issue.

I've replaced the rotor tip, plugs, wires. Still have the miss. Kept the Distr. cap because the miss is completely unbias to weather.
I've replaced the entire fuel pump module and inspected the tank. Still have a stalling issue.

I also have no CEL or error codes to speak of. Any ideas of where to start?

jeepme95 06-19-2008 01:00 PM

Clean and check your throttle body, and IAC. Could also be your CPS which is a pretty common problem and has many of the issues that you are describing. I didnt think a 99 had a distributor cap.

cswetnam 06-19-2008 02:30 PM

99 was the last year of the distributor cap. '00 went to the ignition coils.
Question on the IAC, I have MPI fuel rail. Would the IAC be down by the intake manifold? Not sure where to look. Thanks.

CJ7-Tim 06-19-2008 04:49 PM

What brand/type of plugs did you install ? The Jeep 4.0 doesn't run well with SplitFire or Platinum type plugs. Most Jeep owners use just the plain Champion plugs and get good results.

Use a can of fuel injector cleaner in the next three tanks of gas. Buy the good stuff like SeaFoam or Chevron Techron. - -

Clean the IAC.

There are 3 sensors on the 1997-2001 throttle body -
Bottom - MAP sensor
Middle Right - Throttle Position Sensor (TPS)
Top - Idle Air Controller (IAC)


cswetnam 06-20-2008 05:54 AM

I just put in motorcraft plugs. I'm not super excited about them, but with all of my other issues, it's hard to tell if they're performing as required.

Just pulled the IAC and am in the process of cleaning off the carbon and some junk that's down within that spring loaded metal sleeve. I'll put it back on tonight and change my distributor cap as suggested before. I already have Seafoam on the shelf (love that stuff) to dump in my tank. I'll report back in a day or 2 w/ what I've found. Thanks.

The time now is 04:19 AM.

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