99 Jeep GC Shuts off while driving

[mariner951]

I have 99 Jeep GC, 2WD, 6 cycl, 120,000 mi. Here is the problem. My wife drives the GC and in the last 2 weeks she has reported to me that the GC will just shut off while driving for now reason once or twice during the days travels maybe 3 - 5 times each week and has been getting progessively worse with the system. It shuts off no matter if on the freeway or main city surface streets. I am an A/C mech and a average backyard car mech and I have asked some Q's to my friends on what maybe the problem in the direction to go for troubleshooting. One says batt cables if not grounded well or properly will cause problems or if corroded or frayed wires will definitely be bad and need replaced. I replaced the GC with a new batt 1 mo ago, regular maint. The neg & pos batt cables terminals have some good wear and are most likely OEM, but are not corroded. The terminals will not tighten much more on the posts so, I changed the neg batt cable with a new one, thinking that might the bad cabel. The pos cable is a special order item and I am waiting to get yet. So, I am doing process of elimination, I wanted to replace the batt cables anyways. To me the discrepancy seems to be electrical / fuse related. All the gauges, everything turns off, just nothing. I went to the rescue and meet my wife to look at the problem and it took me approx 30 minutes to get there and once I got there, she had it started again. My Mom mentioned my sister owned a early '80 plym volare and she said it had the same problem. All they did to correct the problem was replace a part called a "Ballest Resistor." Does my 99 GC use this part in the wiring / electrical harnesses in Chrysler vehicles still? It just a stab in the dark as a possible solution considering I have not yet been able to pin point this problem. My wife also says there is no ENG light codes flashing when this happens or when we turn the key to the "ON" position. All the instrument cluster lights extighuish as advertised. It runs tip top once started and running. It starts everytime with the turn of the key. Also, with this discrepancy, could it be associated to the ignition system? I am a do-it yourselfer, so your online diagnosis will be greatly appreciated. Bill

[g1smith]

My 1999 JGC Limited 4.7 started doing the same thing 2 weeks ago, when the tempreture started reaching the upper 90's.

The engine is running smoothly and then it's as if the ignition switch were turned off. Pulling off the road and waiting sometimes five minutes and other times 30 minutes for cooling I suspect. It will then restart and run flawlessly for another 5 miles and then do it again.

Other posters have stated that dealers cannot solve this problem as is intermittant. My dealer says that they have never heard of this problem! It doesn't seem to happen on cooler days or evenings.

When the engine stalls, the gauges on the instrument panel don't seem to have any power;
1. The Volt Meter reads zero volts. It returns to normal or about 12 volts after the engine cools for 30 minutes.
2. The Tempreture Gauge reads zero. It was running at the normal 200 - 210 degrees before it stalled and returns to about 180 after the engine cools for 30 minutes.
3. The Fuel Gage reads zero. It was 3/4 full before the stall and returns to 3/4 after the engine cools for 30 minutes.
4. The Fuel Pump doesn't run for the 1 second prime cycle when the key is turned to the RUN position. Bypassing the Fuel Pump Relay by jumpering connections (30 to 87) causes the Fuel Pump to run continioulsy, but, it will still crank but it won't run.

Does this indicate an ignition problem or a PCM controlled shutdown of the Ignition System?
Bypassing the ASD Relay (30 to 87) and cranking it still doesn't allow it to start and run.
Neither the ASD relay nor the Fuel Pump relay clicks at all while in the shutdown mode. Swapping relays doesn't fix the problem.

Other things do work on the Instrument Cluster while in the shutdown mode. The check engine light, odometer, check gauges, interior & exterior lights, horn, starter, radio, power door locks, power sun roof, . . . but no error codes!

What does the "Instrument Check" refer to. (hold the odo reset and turn on)?

My Crank Position Sensor failed hard about 3 months ago and actually gave me an error code! I replaced it with a $50 one from the dealer and it ran flawless for 3 months before the intermittent stalls began.
I replaced it again with another $50 one from the dealer presuming that I might have a flakey one, but it is doing the same thing.
The outer case on the origional one was made of all plastic, while the replacement one has a metal mounting tab on it where it bolts to the engine. Could this be causing it to absorb more heat?

One poster states that Crank Position Sensors are usually all or nothing, eg, not intermittent.

Another poster states that the Crank Position Sensor is a common problem with all Jeeps and that over time they become temperature sensitive. They need electricity to work and as such, they self heat and can go into thermal runaway which causes both spark and fuel systems to go crazy. Let the vehicle cool off for 20-30 minutes after which it runs like a champ until it heats up again. They're $50 from the dealership and $20 on the internet.

To test the CPS, Crank Position Sensor, one poster states that the Check Engine light will not illuminate at start-up, hence, not allow the engine to fire.

Another poster states that if you don't see your Check Engine Light come on (breifly) when you turn the key to the ON/START Position, then your computer is shot!

I have replaced / checked the following;
1. Fuel pump/delivery (I have replaced the fuel pump),
2. Replaced the CPS (Crankshaft Position Sensor) 3 months ago and fixed a previous no-start problem.
3. Replaced the CPS (Crankshaft Position Sensor) again thinking I got a flakey one from the dealership.
4. Replaced the Camshaft Position Sensor.
5. I've read that the O2 Sensors should measure to 5 - 7 ohms between the two white wires. Mine measure 14 Ohms between the two black wires.
6. I have a K'nN Air filter. Another poster stated that the oil used in these filters can contaminate the MAP sensor. I removed and cleaned the MAP sensor.
7. Removed and measured the TPS (Throutle Position Sensor) throughout the entire range of movement with both a digital and an
analog ohm meter. Meaured smoothe from 5,000 ohms down to 500.
8. Removed and cleaned the IAS (Idle Air Motor).
9. Measured the Engine Coolant Tempreture sensor at 1600 ohms.
10. Measured the Intake Air Tempreture sensor at 3000 ohms.
11. Found the Ground on the engine block, just under the oil and automatic transmision dip sticks, wasn't tight enough for my liking.
Tightnening it didn't fix the problem.

Where are the other grounds located that I should be checking?

12. I don't hear any gush of air when removing the Gas Cap, but neither does any of my other cars.
13. When the PCM (Powertrain Control Module) shuts off power to the ASD and Fuel Pump Relays, is power also droped to the Voltage, Fuel and tempreture gauges on the Instrument Cluster? Are the Crank Position Sensor and Cam Position Sensor the only inputs that can cause the shutdown? What is the timeout period for the Shut Down, 20 - 30 minutes?

14. Coil? My 99 JGC has 8 little high voltage ignition coils build into the individual spark plug caps. I doubt that all 8 are failing at once but could one cause havock with the PCM and cause something like this? Another poster states that the coil has already been changed, twice, which didn't seem to make much difference. They do state that changing out the plugs every 3 months seems to help but believes that's just masking some other problem.

I've read that the electrolytic capicators on the PCM (Powertrain Control Module) age and fail over time. Can these be replaced?

[Jackie Morris]

Originally Posted by g1smith

My 1999 JGC Limited 4.7 started doing the same thing 2 weeks ago, when the tempreture started reaching the upper 90's.

The engine is running smoothly and then it's as if the ignition switch were turned off. Pulling off the road and waiting sometimes five minutes and other times 30 minutes for cooling I suspect. It will then restart and run flawlessly for another 5 miles and then do it again.

Other posters have stated that dealers cannot solve this problem as is intermittant. My dealer says that they have never heard of this problem! It doesn't seem to happen on cooler days or evenings.

When the engine stalls, the gauges on the instrument panel don't seem to have any power;
1. The Volt Meter reads zero volts. It returns to normal or about 12 volts after the engine cools for 30 minutes.
2. The Tempreture Gauge reads zero. It was running at the normal 200 - 210 degrees before it stalled and returns to about 180 after the engine cools for 30 minutes.
3. The Fuel Gage reads zero. It was 3/4 full before the stall and returns to 3/4 after the engine cools for 30 minutes.
4. The Fuel Pump doesn't run for the 1 second prime cycle when the key is turned to the RUN position. Bypassing the Fuel Pump Relay by jumpering connections (30 to 87) causes the Fuel Pump to run continioulsy, but, it will still crank but it won't run.

Does this indicate an ignition problem or a PCM controlled shutdown of the Ignition System?
Bypassing the ASD Relay (30 to 87) and cranking it still doesn't allow it to start and run.
Neither the ASD relay nor the Fuel Pump relay clicks at all while in the shutdown mode. Swapping relays doesn't fix the problem.

Other things do work on the Instrument Cluster while in the shutdown mode. The check engine light, odometer, check gauges, interior & exterior lights, horn, starter, radio, power door locks, power sun roof, . . . but no error codes!

What does the "Instrument Check" refer to. (hold the odo reset and turn on)?

My Crank Position Sensor failed hard about 3 months ago and actually gave me an error code! I replaced it with a $50 one from the dealer and it ran flawless for 3 months before the intermittent stalls began.
I replaced it again with another $50 one from the dealer presuming that I might have a flakey one, but it is doing the same thing.
The outer case on the origional one was made of all plastic, while the replacement one has a metal mounting tab on it where it bolts to the engine. Could this be causing it to absorb more heat?

One poster states that Crank Position Sensors are usually all or nothing, eg, not intermittent.

Another poster states that the Crank Position Sensor is a common problem with all Jeeps and that over time they become temperature sensitive. They need electricity to work and as such, they self heat and can go into thermal runaway which causes both spark and fuel systems to go crazy. Let the vehicle cool off for 20-30 minutes after which it runs like a champ until it heats up again. They're $50 from the dealership and $20 on the internet.

To test the CPS, Crank Position Sensor, one poster states that the Check Engine light will not illuminate at start-up, hence, not allow the engine to fire.

Another poster states that if you don't see your Check Engine Light come on (breifly) when you turn the key to the ON/START Position, then your computer is shot!

I have replaced / checked the following;
1. Fuel pump/delivery (I have replaced the fuel pump),
2. Replaced the CPS (Crankshaft Position Sensor) 3 months ago and fixed a previous no-start problem.
3. Replaced the CPS (Crankshaft Position Sensor) again thinking I got a flakey one from the dealership.
4. Replaced the Camshaft Position Sensor.
5. I've read that the O2 Sensors should measure to 5 - 7 ohms between the two white wires. Mine measure 14 Ohms between the two black wires.
6. I have a K'nN Air filter. Another poster stated that the oil used in these filters can contaminate the MAP sensor. I removed and cleaned the MAP sensor.
7. Removed and measured the TPS (Throutle Position Sensor) throughout the entire range of movement with both a digital and an
analog ohm meter. Meaured smoothe from 5,000 ohms down to 500.
8. Removed and cleaned the IAS (Idle Air Motor).
9. Measured the Engine Coolant Tempreture sensor at 1600 ohms.
10. Measured the Intake Air Tempreture sensor at 3000 ohms.
11. Found the Ground on the engine block, just under the oil and automatic transmision dip sticks, wasn't tight enough for my liking.
Tightnening it didn't fix the problem.

Where are the other grounds located that I should be checking?

12. I don't hear any gush of air when removing the Gas Cap, but neither does any of my other cars.
13. When the PCM (Powertrain Control Module) shuts off power to the ASD and Fuel Pump Relays, is power also droped to the Voltage, Fuel and tempreture gauges on the Instrument Cluster? Are the Crank Position Sensor and Cam Position Sensor the only inputs that can cause the shutdown? What is the timeout period for the Shut Down, 20 - 30 minutes?

14. Coil? My 99 JGC has 8 little high voltage ignition coils build into the individual spark plug caps. I doubt that all 8 are failing at once but could one cause havock with the PCM and cause something like this? Another poster states that the coil has already been changed, twice, which didn't seem to make much difference. They do state that changing out the plugs every 3 months seems to help but believes that's just masking some other problem.

I've read that the electrolytic capicators on the PCM (Powertrain Control Module) age and fail over time. Can these be replaced?

my 1997 was dying similar to that and it would die in the mornings when I had it running to warm up, it finally died completely and it was the computer on it, $200 at Napa. I had replaced everything trying to fix it until it died.