Questions and Answers

Jeep Cherokee Dies In The Heat Q. Okay, here's my stalling story, I have a 1993 Jeep Cherokee with 160,000 miles which ran very well with no problems until three days ago. I like everyone else with this problem took it to a mechanic. and he checked the throttle body cleaned it, changed the fuel filer, changed the Crankshaft Position Sensor (CPS) but still stalls.

He also checked the psi of the fuel pump, put the car on a diagnostic machine, no codes. Also checked and changed the relays in the fuse box under the hood. Pulled on every wire harness, still stalls but only when driving. You can leave the car in idle and never stalls.

Now here's the thing, I did some testing with friend while the car had stalled with the key still in the on position the car would not start, so we pulled a spark plug wire and put a screwdriver bit inside the plug and held it to the engine cranked the car and no spark.

So I turned off the ignition and waited about 20 to 30 (minutes?) the jeep started right up and there was spark coming from that wire. I hate to be long winded but i am trying to keep costs down and have not replaced the main PCM, coil or fuel pump. Could a blocked catalytic converter also cause this no spark thing after the jeep has stalled? Is there something tripping the auto shutdown relay??

• 1993 Jeep Cherokee
• 4.0 liter
• Automatic transmission
• 160,000 miles
• Fuel injection

Thanks for any help,
Bill

A. First off, a bad catalytic converter will not cause a no spark condition.

These checks must be done when the vehicle won't start or they will not help track down the problem. If you look at the wiring diagram, you should have power to the dark green/orange wire at the coil. This is the feed from the ASD relay.

Flashing the black/gray wire to ground should generate a spark from the coil wire. If it does, the ASD relay and coil are good. If you flash the gray wire at the PCM connector and generate a spark, everything up to the PCM is good.

All that leaves is the Crankshaft Position Sensor (CPS), the wiring or the PCM itself.

	To test the CPS, near the rear of intake manifold, disconnect the sensor harness connector from the main wiring harness. Place an ohmmeter across terminals B and C.
Ohmmeter should be set to 1K-to-10K scale for this test. The meter reading should be open (no resistance). Replace the sensor if a low resistance is indicated.

If all of this checks out good, you probably have a bad PCM. You might also want to read Handling No Trouble Code Problems.