Questions and Answers

Jeep Cherokee Laredo Starts And Stalls Q. Good afternoon. I have a 1989 Jeep Cherokee Laredo 4x4, 4.0 liter and automatic transmission. The problem I'm having is that the engine starts with little coaxing and after 10 minutes idling in the driveway looks like any other decent running car. The problem begins when I put the car in DRIVE, it stalls.

To get it to drive I have to rev it really high. But as soon as I stop it dies again. It will also send the temperature through the roof. I don't want to damage my engine. I believe the problem to be one of a few different things.

1. PCV system is clogged causing a vacuum problem.
2. Ignition sensor is bad.
3. Seriously needs a tune up.
4. Seriously needs a new engine.

A little history on the Car. I bought it for $600.00. I expected problems, so fixing it was already in the budget. It sat for about a year in a driveway before I bought it but was started regularly. The owner never had any problems like this before, of course not, and doesn't know what it could be.

I don't want to bring this thing to a mechanic. I believe I can do the work myself I just need to know where to start. There is also oil in the air filter which is making me believe the PCV system is clogged. What should I do? Also, There is a little switch below the steering column. What is that?

Mike

A. This was a widespread problem for Chrysler and they issued a couple of TSBs to address the problem. The first was:

Models:
1989 MJ & XJ Bodies

Subject:
4.0L No-Start, Hard Restart, or Engine Die-Out. Vehicles Equipped With Automatic Transmission Only.

Index:
DRIVEABILITY

Date: December 29, 1989 No.: 18-57-89 (C18-23-9) P-14

Body Code Legend:
MJ - COMANCHE (RWD, 4WD) XJ - CHEROKEE/WAGONEER (RWD, 4WD)

SYMPTOM/CONDITION:
Some 1989 vehicles equipped with the 4.0L engine and automatic transmission may experience an engine no-start, hard restart, or an engine die-out. This condition may be caused by low signal strength from the crank position sensor due to a larger than desired distance to the flywheel sensing ring.

DIAGNOSIS:

Check to see if the vehicle has a slotted crank position sensor:

1. 1. If the vehicle is equipped with a slotted crank position sensor (see Figure 1), check to see if the CPS grommet on the top of the transmission bell housing has been updated (see Figure 2). If the CPS grommet has not been updated, replace the CPS grommet per the Repair Procedure outlined below.

If the vehicle has a slotted crank position sensor and new CPS grommet, do not install a new sensor, but reinstall the slotted sensor that was on the vehicle and verify that it is good using procedures in the 1989 Jeep Service Manual 81-370-9045 on page 14-87.

2. 2. If the vehicle does not have a slotted crank position sensor already installed, then proceed with the Repair Procedure.

PARTS REQUIRED:

1	Crank Position Sensor (slotted)	P/N 83100067
1	Crank Position Sensor Grommet	P/N 83100068

REPAIR PROCEDURE:

1. Turn the ignition switch to the "OFF" position.
2. Disconnect the Crank Position Sensor (CPS) from the engine harness.
3. Raise the vehicle using a lift.
4. Remove the old CPS and grommet.
5. Install the new CPS grommet.

NOTE: THE NEW CPS GROMMET MUST BE REPLACED SO THAT THE MAXIMUM SIGNAL OUTPUT CAN BE OBTAINED FROM THE NEW CRANK POSITION SENSOR.

6. Install the new Crank Position Sensor and loosely attach the retaining bolts.
7. Firmly press down on the slotted hole side of the CPS until it bottoms on the machined lip of the bellhousing. While holding the CPS down against the bellhousing, tighten the bolt on the slotted side of the CPS to 16 ft.lbs.
8. Tighten the remaining attaching bolt to 16 ft.lbs.

NOTE: MAKE CERTAIN THAT THE CRANK POSITION SENSOR IS COMPLETELY BOTTOMED ON THE MACHINED LIP OF THE BELLHOUSING AND IS AS CLOSE AS POSSIBLE TO THE FLYWHEEL SENSING RING WITHOUT CONTACTING IT.

9. Secure the lead of the CPS to the retaining clip on the bellhousing to prevent its contact with the exhaust manifold.
10. Lower the vehicle.
11. Connect the CPS to the engine harness.

If this repair has been made, or hasn't fixed the problem, the other TSB is 18-54-89 REVISION A recommending cleaning of the throttle body assembly, DIY: Cleaning Throttle Bodies, and replacement of the PCM.

PARTS REQUIRED:

1	ECU (Automatic Transmission)	P/N 53007842
1	ECU (Manual Transmission)	P/N 53007843
1	Mopar Choke and Linkage Cleaner	P/N 4549619

As for that little switch under the steering column, I have never seen a Jeep with a switch such as you describe. It may be a home made "security system" and could be causing your problems. As for your other concerns...

1. Replace the PCV valve and check all the hoses for proper attachment and leaks. A leaking PCV hose could cause the problem as well.
2. Addressed in the above TSBs.
3. Go ahead, it can only help
4. I seriously doubt it, but I would do a wet/dry compression test just to be sure.