My 1999 GC 4.7 V8 stalls when the weather is hot. The engine is not overheated. The engine temperature guage does not show that it is overheated. When the engine restarts it starts easily and runs fine.

Driving time, speed, RPM, etc. do not seem to matter. I suddenly loose guages and the engine shuts down immediately- no sputtering or chugging. The "check guages" light comes on. I have noticed the "transmission overtemp" light comes on as I restart, but I think this light comes on everytime the engine is started and then it shuts off shortly after starting.

After I open the hood and let it cool 5-40 minutes (cooling time required is quite variable) it will start and run fine. I get no codes left in the computer.

I have replaced the crankshaft position sensor but as yet so far have not had a chance to drive it again in a hot climate to test the fix.

I speculate that possibly the fuel line may be getting overheated and causing vapor lock but with no sputtering and a hard shut down I really don't think this is likely- does anyone have experience with this as a cause for the problem?

I have read that a bad ASD auto shut down relay can cause this problem, but have not checked mine yet. Also, the relay may be fine but receiving a signal to shut down. As noted above I get no computer codes - I'm using a simple Checker Auto code reader and don't know if different readers are capable of reading more codes or not.

Based on what I've read so far I think that something is causing the ASD relay to shut off the engine. Possibly a sensor is prone to failure in hot weather??? Does anyone know what sensors, etc. can shut down the ASD relay, and how to test for which is causing the problem?

I have a long vacation drive coming up and would like to fix this before I leave. Thanks in advance for any advice you can give me.

 

Usually the "Check Gauges" light comes on to bring your attention to one of your gauges. Either the Engine temp., oil pressure, charging system., is out of normal range. The only guess I have is the engine was hot and caused a heat soak condition in the fuel rail. Our '04 WJ w/the 4.7 was purchased new and has never experienced a similar occurrence in 89,000+ miles.
Do any of these TSB's cover your situation?
And Welcome to CF!
Dan

 

I just had another shutdown. This time it was in town after a couple of stop and restarts. I don't think there is any way that anything could have been overheated. Ambient temp is cool.

This time I happened to be watching the guages. I actually lost power while the guages were still functioning properly. I must have caught it at the exact moment of shutdown. Guages looked good, I pressed the accelerator and nothing happened- I realizied the engine must not be running. Then moments (like 1/2 to 1 second) later the guages all started to go to zero.

On attempts to restart I noted that when the ignition was turned on, no guages came up on failed attempts to restart.

Then after about 5 min. I turned the ignition on but not all the way to start and the voltage, fuel, and temp. guages came up. When I turned the key further to start then everyting started as normal. The Jeep ran fine again and I stopped and restarted sucessfully 2-3 times before returning home.

 

I have actually thought of putting some Isopropyl Alcohol in a spray bottle and quickly spraying the fuel rail to cool it and see if the engine starts sooner.

My other thought is to spray the fins on the computer module to see if it fixes the problem.

I am wondering about the possiblility of a ground wire being loose but haven't checked it yet. Does anyone know if this is a likely culpret? It seems logical, but the many failures and restarts without jiggling any wires makes me think this is not a particularly likely cause.

 

I'm at a loss here. Hopefully someone else will chime in with some helpful advice.
Dan

 

It is possible that you my have some ignition wire loose.

 

I was checking fuses and noticed that in the PDC (power distribution center) by the battery I have two relays missing. They must have been missing since before I purchased the vehicle used from a dealer in June 2002.
The missing relays are #34-Rear O2 Sensor and #35-Front O2 Sensor.

I think there is a bridge between the O2 Sensors which will cause the ASD (auto shutdown relay) to turn the engine off if the differential voltage between the two sensors is out of spec.

Is it possible the ASD relay is getting a shutdown signal because of the O2 sensor differential voltage, but I am not getting a diagnostic code because the relays are not in place????

I have noticed before that my reader says no diagnostic codes are present but the C (catylist), EV (evap system), and O (oxygen sensor) indicators keep blinking which I think indicates that the test was not or could not be performed.

 

This shows a different function for relay # 35, and it's empty also.... http://www.wjjeeps.com/misc/power_dist_ctr_02.jpg
I don't know what difference it makes though. I still don't have an answer for your issue.
Dan

 

I'm sure it is possible, but I don't think likely since the jeep always restarts after cooling without any wire jiggling or other manipulation.

I have noticed my ignition switch does not always spring back all the way after starting and am aware of the tendancy for the switch to go bad- I always make sure it it rotated back where it is supposed to be in running mode.

I have considered replacing the switch, but have not got to it yet. Acually I looked at the assembly drawing and cannot dicern how the spring return action is accomplished- I think it may be done by the electrical portion of the switch and not the keyed portion.

 

I got the relay functions from reading the "relay map" located under the cover of the PDC. It clearly states the relay numbers and functions as I indicated.

Is your hypertext for the PDC photo for a 1999 Grand Cherokee V8 - 4.7 Liter?

 

It's from this site: http://www.wjjeeps.com/

 

hi, im beem experiencing the sam eproblems with my jeep, i can t find the fix yet. please let me know any update you find i will really apreciate it, as i can see everyone on other blogs are very selfish and dont post the fix after they found the problem. i have another place to look if you can email me at pedrosainz@hotmail.com and we can comunicate directly and be updated to fix this problem togueter and help out others. thanks

 

please email me at pedrosainz@hotmail.com i can help you fix your jeep

 

Hey pedro, Welcome to CF!

 

I had stalling problems as well and it turns out it was a bad ASD relay. Swapped out and all seems to be well now....