99 Intermittent Total Elec Fail & Won't Idle

This is a weird one, I searched, couldn't find anything quite like it. Occaisionally when I try to start my 99 XJ (4.0, AW4), when turning the key I'll get an initial click from the starter as though the solenoid begins to engage, and then everything on the rig dies. Lights, radio, gauges, etc. As though some one has disconnected the negative battery terminal. Recycling the igniton switch will bring it back to life, but sometimes I have to recycle it 4-5 times. I drive with my odometer set on trip, when it comes back to life the odometer will read the "total" reading, and sometimes the clock (on the radio) will reset to 12:00 (but radio presets are still there). Most of the time that this occurs, when the rig comes back to life and I start it, it won't idle. It runs fine, but if I take my foot off the gas, it dies. I can keep it running by lightly pressing the gas, riding the brake, and shifting between D-R and N to get going. Once I'm out on the road, 30 sec to 1 min of driving and all is ok again.

The only other thing I can correlate it with with is moisture, it seems as though this occurs most often if there has been a rain or heavy dew, but I live in a a desert area and that doesn't happen much. It did happen a day or two ago when the weather had turned quite a bit cooler than it has been, but maybe that caused a bit of condensation or something.

I know just enough about TPS, NSS and CPS problems to be dangerous, but none of those (that I know of) cause this electrical blackout, they just make the rig not start, not idle, or die. I don't get any kind of CEL or trouble codes.

Any input anyone has would be greatly appreciated. No one really knows MoPar in my area and I'm a long way from anywhere else. It's kind of hard to diagnose (like any intermittent problem) b/c if it's not doing the problem at any particular time then I'm not sure there's any point in driving two hours to see someone who might be able to diagnose it.

I'm not a very active member, mostly becasue I don't really have enough knowledge to contribute much, but this is an awesome resource and has been a lot of help to me in the time I've owned my XJ.

motorob said:

Most of the time that this occurs, when the rig comes back to life and I start it, it won't idle. It runs fine, but if I take my foot off the gas, it dies. I can keep it running by lightly pressing the gas, riding the brake, and shifting between D-R and N to get going. Once I'm out on the road, 30 sec to 1 min of driving and all is ok again.

Click to expand...

Above is the biggest clue to me from your post.....it appears that your computer is re-learning it's idle, etc after this happens. The re-learning is what happens when you change or disconnect your battery. I would concentrate on the battery itself AND all connections/wiring associated with the battery. Freshen all connections including grounds, even if they look okay. Have the battery load tested as low available battery voltage can create these type of symptoms. Keep us posted.....

Indeed the problem here was bad battery connections. I should have responded to birchlake's response much sooner, and I apologize for that. I got distracted and didn't come back to this post for a while.

I caution anyone experiencing starting/idling problems to check their battery at one of the earliest steps in your troubleshooting process. This was especially comlicated for em as my problem only occurred during periods of high humidity, and I live in a place that sees ~ 8" of rain/year and most of that occurs in a 6 week period. It was impossible to duplicate the problem by wetting the vehicle down with a hose or anything like that (I tried.) But we have expeienced rain for the last 48 hours or so and I have had no trouble after removing, cleaning thoroughly and reinstalling my battery terminals.

I don't use this forum a lot as my XJ is pretty mild and I don't have a lot of trouble with it, but when I do, what a great source of info. Donation on the way!

motorob,

Glad to hear the problem was something as simple as battery connections.

The importance of a solid electrical system should never be overlooked for symptoms like you described.......poor idle/dying engine.

Enjoy your XJ!