trys to stall while driving

I have a 94 xj 4.0L auto 4wd 175k miles. I can be driving down the road and it will feel like the engine dies out, I can pat the gas pedal a few times and it will give a spark knock noise (valves rattleing), then pick right up and smooth out like there is nothing wrong. Only happens on long trips and about every 15-20 miles, only completely shut off one time and it was while it was idling. Started right up and ran great again. No check engine light on. Im worried its gonna strand me somewhere if I dont get it fixed before it really quits. Any help would be greatly appreciated, Thanks.

If the engine just "dies" momentarily, the prime suspects are the crankshaft position sensor and the ignition coil with the crank sensor failing in this manner far more frequently than the coil.

Both can be tested for resistance values but know that with this type of intermittent problem, the component "could" test good if tested when the vehicle is running. If however it is out of spec or close to being out of spec, it should be replaced.

Here's more on the crank sensor...

Crankshaft Position Sensor: (CPS/CKP) Failure Symptoms / Testing

*Both the fuel gauge and or voltage gauge may not work/display

*It is possible that you may see a No Bus on the odometer (on newer models only)

*You will have no spark. Fuel pressure may check out okay at the fuel rail, but fuel won’t get to the fuel injectors

*For 96 + newer, sometimes the OBDII code reader has trouble connecting to /reading codes. Crankshaft position sensor failure may or may not result in a check engine light/fault code.

*Crankshaft position sensors can be intermittent resulting in an abrupt misfire. "Thermal failure" is common. Thermal fail means that the sensor fails when engine gets hot, but works again when engine cools down. Be aware of this when testing, as if you have a sensor that suffers from thermal failure, it’s possible that it may test GOOD as soon as it cools down.

*Don’t get tunnel vision and assume the sensor is bad (unless it checks out as bad with a meter) Damaged wiring or a dirty connector can inhibit the signal from making it to the computer. Check/clean/repair as necessary. Use electrical contact cleaner for the connector, put a dab of dielectric grease on it before reconnecting.
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CRANKSHAFT SENSOR TESTING PROCEDURE: 1991 – 2001 4.0L H.O. engines

1. Near the rear of intake manifold, disconnect sensor pigtail harness connector from main wiring harness.

2. Place an ohmmeter across terminals B and C. The terminals are identified as A-B-C looking into connector from left to right with the "notch" in the middle of the connector on your right. Ohmmeter should be set to 1K-to-10K scale for this test.

3. The meter reading should be open (infinite resistance). Replace sensor if LOW RESISTANCE

any other ideas?