2001 Other Jeep Models 2001 Jeep Grand Cherokee Laredo

JERRYBUD33

MEMBER
2001 JEEP
6 CYL
4WD
AUTOMATIC
123,000 MILES

I have a 2001 JGC Laredo with 123000 miles. This past weekend the engine stalled (died!) While I was at a stop light. Was able to get it started after several attempts and drove 20 miles without issue. Later that night as I was driving home the engine died again while the car was traveling at 55mph-- I noticed that he car "hiccupped" slightly right before it died. Was unable to get it restarted and had it towed. The battery was fine and I had all lights, but the car would not turn over. The next day my mechanic called and told me that the Jeep started right up in the morning. My mechanic tested the fuel pump, fuel filter, etc. And did not find any problems. He also did a diagnostic check and did not get any error codes. He let the car idle for over an hour and there were not any problems. He drove the car around and stated that the car drove fine, no loss of power, no idling issues, no problems at all! I had the fuel filter replaced anyway, and a fuel additive was used in case there was water in the line/tank. The car drove home without issue. After being home for about 45 minutes I went out again to move the car. I took three tries before it started. I decided that I would let it run for a while, and after about 15 minutes the engine quit, but restarted on the first try. I let the car run a little longer and took it for drive, without issue. In the morning (very cold morning) the car started no problem, and I drove to work without issue. I left for lunch, car started, but then just died again -- and restarted after two attempts and drove fine. Has my mechanic overlooked something? Is there something that could be plugged/blocked/failing that would not show up as an error code on the diagnostic machine? Any help would be greatly appreciated. I travel alot for work and need a car that stays running!

3 Replies

JNOVACK

MECHANIC
723 POSTS

Take jeep to dealer and have them test the pcm there is a recall for pcm to be reprogramed that can and will cause this issue

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Tuesday, December 9th, 2008 AT 6:37 PM

JERRYBUD33

MEMBER
2 POSTS

Would a faulty/bad PCM show up on the original diagnostic? As I stated in my original question, the Jeep was put on the machine and no error codes came up. Also, from my research, the recall on the PCM was for up to model year 2000. If not the PCM, could it be something like an Idle Air Control valve, or a faulty MAF sensor? The Jeep continues have the same problem, except now when it dies the check gauges/engine light does not come on. HELP!

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Monday, December 15th, 2008 AT 11:41 AM

JNOVACK

MECHANIC
723 POSTS

Removal & Installation

3.7L & 4.0L

The TPS is mounted to the throttle body.
Disconnect TPS electrical connector.
Remove TPS mounting screws.
Remove TPS.
To Install:

The TPS is mounted to the throttle body. The throttle shaft end of throttle body slides into a socket in the TPS. The TPS must be installed so that it can be rotated a few degrees. (If sensor will not rotate, install sensor with throttle shaft on other side of socket tangs). The TPS will be under slight tension when rotated.

Install TPS and retaining screws.
Tighten screws to 7 Nm (60 inch lbs.) torque.
Connect TPS electrical connector to TPS.
Manually operate throttle (by hand) to check for any TPS binding before starting engine.

4.0L

The Crankshaft Position Sensor (CKP) is mounted to the transmission bellhousing at the left/rear side of the engine block. Engine speed and crankshaft position are provided through the crankshaft position sensor. The sensor generates pulses that are the input sent to the powertrain control module (PCM). The PCM interprets the sensor input to determine the crankshaft position. The PCM then uses this position, along with other inputs, to determine injector sequence and ignition timing. The sensor is a Hall effect device combined with an internal magnet. It is also sensitive to steel within a certain distance from it.

On 4.0L 6-cylinder engines, the flywheel/drive plate has 3 sets of four notches at its outer edge. The notches cause a pulse to be generated when they pass under the sensor. The pulses are the input to the PCM. For each engine revolution there are 3 sets of four pulses generated.

The trailing edge of the fourth notch, which causes the pulse, is four degrees before top dead center (TDC) of the corresponding piston. The engine will not operate if the PCM does not receive a crankshaft position sensor input

4.0L

The Camshaft Position Sensor (CMP) on the 4.0L 6cylinder engine is bolted to the top of the oil pump drive shaft assembly. The sensor and drive shaft assembly is located on the right side of the engine near the oil filter.

The CMP sensor contains a Hall effect device called a sync signal generator to generate a fuel sync signal. This sync signal generator detects a rotating pulse ring (shutter) on the oil pump drive shaft. The pulse ring rotates 180 degrees through the sync signal generator. Its signal is used in conjunction with the crankshaft position sensor to differentiate between fuel injection and spark events. It is also used to synchronize the fuel injectors with their respective cylinders.

When the leading edge of the pulse ring (shutter) enters the sync signal generator, the following occurs: The interruption of magnetic field causes the voltage to switch high resulting in a sync signal of approximately 5 volts.

When the trailing edge of the pulse ring (shutter) leaves the sync signal generator, the following occurs: The change of the magnetic field causes the sync signal voltage to switch low to 0 volts.

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Monday, December 15th, 2008 AT 1:37 PM