[241comp]

Ok, I've got a '99 with the 4.7L and recently I fixed the AC. Upon fixing, I discovered that the Jeep would overheat when the AC was running and it turned out to be the fan relay which I have replaced. Both the electric and mechanical fans are running properly now but I am still having problems. The first time that the Jeep got too hot (before I fixed the fan relay), it stalled and I assumed that this was due to vapor-lock because the temp gauge was reading around 230-ish.

Since fixing the electric fan, it hasn't gotten more than a hair over 210 and it still stalls on me! When I'm driving around town in warm weather (70's-80's), the gauge will slowly creep to 210-212 and suddenly the entire dash goes dark, the gauges freeze and the car stalls. The check engine light doesn't come on and there are no codes. It turns over fine but won't start until I give it a good 5-10 minutes to cool down. I'm planning to have the alternator tested tomorrow though it doesn't have any alt-specific symptoms. This doesn't happen when it is cool out (50's-60's). Other than that... I'm at a loss. Any ideas what might be wrong? Help!

[rm2001wj]

I would consider replacing the automatic shut down (ASD) relay. Since the problem is intermittent, it would be a little difficult to actually test it.

[241comp]

Ok, I'll try the ASD relay. I'm assuming I'll be able to find it pretty readily - is it a standard relay or something I'm going to need to get from the dealer?

Any other suggestions to try while I'm at it?

[rm2001wj]

The relay is in the power distribution center under the hood. It's the black box, longer than it is wide, next to the battery. I'm pretty sure there is a labeled diagram inside the lid. I don't know if you can get a replacement from a parts store like AutoZone or not. I wish that I could guarantee replacing it would fix you problem, but I can't.

[241comp]

Alright, that's replaced. I'll take it for a drive this evening and see if I can get it to stall out or not. I'll post back my results.

[241comp]

Well, I took the Jeep out and it stalled again. I was sitting in the parking lot idling while my wife shipped a package and it stalled. The guages froze, dash shut off and the Jeep engine shut down. A few seconds later, the guages all went to zero. I let it cool for a few minutes and it ran fine for the rest of our evening out - no more stalling. So, it appears it wasn't the asd relay. Any other possibilities?

[rm2001wj]

Sorry that the new ASD relay didn't solve the problem. I'm not going to suggest anything else if it involves buying a new part. But, I suspect other suggestions might be along the same lines.

[241comp]

Feel free to make more suggestions - I didn't even have to buy the relay to replace the ASD because it fits a standard Bosch 30A. Anyway, I've swapped it back for now. I was thinking maybe crankshaft sensor? Anyone?

[Bob D.]

it turned out to be the fan relay which I have replaced.

Herein may lie your problem. From your first post it sounds like the fan relay: ("the gauge will slowly creep to 210-212 and suddenly the entire dash goes dark, the gauges freeze and the car stalls.")

210-212 deg. is where the relay is instructed by the PCM to run at high speed. Since it was just replaced, it's possible the relay is defective and shorts or feeds back some bad info to the PCM when it gets the run on high signal.
I don't know how you would diagnose that, except to disconnect the electric fan relay and let it run in your driveway until it gets to 212-215 and see if it stalls.

[zjhitman]

Have you checked out the battery? Terminals cleaned, water checked, load tested etc? I drive a ZJ so I have no experience with the WJ except reading this forum but maybe I can suggest some things to check. I can't guarantee these are WJ related, but things that come to mind. There is something called a Battery Temperature Sensor that sits underneath the battery tray that I think prevents the battery from starting the engine if the underhood temp is too high. I have also read about a Body Control Module that I believe controls most of the non-engine related electrical components. I don't think a bad CPS would cause the dash gauges to freeze and loose power. It almost sounds like there is a temperature controlled circuit breaker under the hood that is tripping and resetting dependant on temperature. The dash gauges freezing and going dark is a new one for me. Don't think I have seen it mentioned here before. You need some WJ guys to help nail this one. Keep us updated.

[241comp]

Originally Posted by Bob D.

Herein may lie your problem. From your first post it sounds like the fan relay: ("the gauge will slowly creep to 210-212 and suddenly the entire dash goes dark, the gauges freeze and the car stalls.")

210-212 deg. is where the relay is instructed by the PCM to run at high speed. Since it was just replaced, it's possible the relay is defective and shorts or feeds back some bad info to the PCM when it gets the run on high signal.
I don't know how you would diagnose that, except to disconnect the electric fan relay and let it run in your driveway until it gets to 212-215 and see if it stalls.

I have been running the AC to get the engine temps up fast when trying to get it to stall so the fan is running the entire time (comes on when the AC is turned on). Also, this problem was happening before when I had a bad PCM in the vehicle (so no elec. fan), just not as often. Also, I should say, it doesn't stall every time it gets to 212 - just sometimes. And it has to be there for at least 5-10 minutes before it stalls. Then it might run for another hour without stalling again. So it is intermittant, whatever it is.

Originally Posted by zjhitman

Have you checked out the battery? Terminals cleaned, water checked, load tested etc? ... There is something called a Battery Temperature Sensor that sits underneath the battery tray that I think prevents the battery from starting the engine if the underhood temp is too high. ... It almost sounds like there is a temperature controlled circuit breaker under the hood that is tripping and resetting dependant on temperature. ... Keep us updated.

I checked the battery terminals (cleaned and re-seated cables) first thing. I'll have the battery tested today. Regarding the Batt Temp Sensor, would this prevent the vehicle from turning over or just prevent it from starting? It turns over fine when it stalls - just won't start until I let it cool for a few mins. The dash guages shutting off, I assume, comes from the fact that the engine dies. I could try stalling the engine intentionally (cover air intage or something) and see if the gauges behave the same.

I've got a fuel press gauge kit on order so I can see if I'm getting fuel when it refuses to start. Is there a good way to check for spark with the coil system the WJ has? I'll keep y'all updated on my progress. Any further suggestions are welcome!

[rm2001wj]

With the instrument cluster going dark, I'm pretty sure that the problem is not due to any particular sensor going bad. Instead, the PCM is starting to become suspect. While working on the the AC, fan relay, etc., did you ever unplug the PCM? I have heard of the connector making a poor (and intermittent) contact on one or more pins even if the harness has not been unplugged.

Next time it stalls and then won't start, raise the hood and try to wiggle the PCM harness and connector a little. Do this with the key in the ON position and see it the instrument cluster comes back to life. If that doesn't work, try wiggling anything electrical that you can get you hands on.

Something else that might be worthwhile to do, when the instrument cluster is on with the key in the ON position, is to the wiggle things and see if the cluster goes dark. In other words, test for a poor connection before the cluster goes dark.

[241comp]

Originally Posted by rm2001wj

With the instrument cluster going dark, I'm pretty sure that the problem is not due to any particular sensor going bad. Instead, the PCM is starting to become suspect. While working on the the AC, fan relay, etc., did you ever unplug the PCM? I have heard of the connector making a poor (and intermittent) contact on one or more pins even if the harness has not been unplugged.

Next time it stalls and then won't start, raise the hood and try to wiggle the PCM harness and connector a little. Do this with the key in the ON position and see it the instrument cluster comes back to life. If that doesn't work, try wiggling anything electrical that you can get you hands on.

Something else that might be worthwhile to do, when the instrument cluster is on with the key in the ON position, is to the wiggle things and see if the cluster goes dark. In other words, test for a poor connection before the cluster goes dark.

Thanks for the suggestions - I'll give them a try. I didn't disconnect the PCM but I can try disconnecting it and checking the contacts for corrosion. I suppose this would be a good time to get some dielectric grease on those contacts anyway. I should specify - the gauges go dark like I've turned off the car. If I turn the key to the off position and to on again, everything comes right back up with no delay... doesn't seem like the same electrical connection problem causing both since although the dash comes back online, the engine still won't start.

[241comp]

I have an update to report. I had been reading the codes with my Actron OBD-II (e-bay, $50, great investment) reader and getting nothing after each time it stalls. This time, however, was different. I got code P0725 which indicates a problem with the Engine Speed Sensor (also known as the Crank Position Sensor)! So, I'm going to replace the CPS when it comes in (ordered today) and see if I can still get the car to stall for me.

I spent some time today inspecting and cleaning all of my electrical connectors and adding dielectric grease... while I was under the car doing the brake sensor connectors, I noticed that the ground strap between the frame, exhaust and transmission(?) is broken. How important is that strap?

[zjhitman]

Ground straps anywhere on a GC are very important. If they are missing or damaged, they can cause you a world of grief. See what happened to mine in the attached link. http://www.jeepforum.com/forum/f13/wierdest-driveability-problem-i-ever-had-happen-235432/