97 XJ won't idle or rev over 2000 rpm

Hi,
I picked up a 97 xj last weekend with the previous owner saying it had no spark and he had put in a new coil and CPS with no luck.
The passenger engine mount had broken off and the engine was resting on the distributor which it bent and seized so the distributor gear broke.
I pulled what I could find of the gear out of the oil pan, put a new distributor assembly in, and the engine fired up and after reving idled decently. Tried driving and once it heated up it ran badly, wouldn't idle and anywhere above 2k rpm it's as if it's hitting a rev limiter.
Also pulled the codes p1391 and p0320 so I thought it was the new cps or cam sensor in the distributor. I swapped both back to the originals and the issue persists, still giving those codes. I've measured the resistance from battery ground to the group terminals of both sensors and it's under 1 ohm so I have no idea what it could be. The battery is brand new.
Hoping anyone might have an idea of where to start to figure out whats wrong with it? I also started it this morning before swapping the sensors and it ran nicely but it was cold

Tps, always the first place to look. No matter what the problem is. Not shifting? Tps. Cruise not working? tps. Flat tire? Yep, check that damn tps.

My 96 would idle and drive OK for a few minutes but as soon as it switched from open to closed loop it would hardly idle, sometimes wouldn't rev, and would sometimes just die. It turned out to be the O2 sensor, It never did throw a MIL code for the O2 sensor.
Also possible you're a tooth off with the distributor.

Use the Check Engine Light Light trouble codes to focus and guide your diagnostics. Your Jeep has on-board diagnostics and is trying to tell you what is wrong.

If diagnostics and testing of the existing trouble codes are not successful in solving the issues, test the fuel pressure and as suggested test the TPS.

CPS wiring up against the exhaust from the engine sitting crooked? Dist indexed corrected and plug wires in the right spot?

One tip, try to purchase Mopar sensors the chinese ones are known to be a problem.

Unclewolverine said:

Tps, always the first place to look. No matter what the problem is. Not shifting? Tps. Cruise not working? tps. Flat tire? Yep, check that damn tps.

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Just checked the tps, it start at around 0.8v and has a smooth curve up to 3.95v so I think it's good.

even when cool the jeep doesn't idle at start up anymore, so I'm thinking I may try swapping back the "replacement" cps and if it idles before warming up I'll know that somehow both cps were bad and order a new mopar one

8Mud said:

My 96 would idle and drive OK for a few minutes but as soon as it switched from open to closed loop it would hardly idle, sometimes wouldn't rev, and would sometimes just die. It turned out to be the O2 sensor, It never did throw a MIL code for the O2 sensor.
Also possible you're a tooth off with the distributor.

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Would it idle at all with a tooth off? It was running decently a couple times when cool before, but if it's possible to idle while that far off I'll maybe try the distributor one tooth in either direction and see if that helps

lawsoncl said:

CPS wiring up against the exhaust from the engine sitting crooked? Dist indexed corrected and plug wires in the right spot?

Click to expand...

CPS wire looks good and nowhere near the exhaust, and I believe dist is indexed correctly since I had it idling briefly before, wires are correct

Wondering what diagnostics and testing of the p1391 and p0320 have discovered ? The symptoms being related to temperature suggests a faulty engine sensor.


P0320 JEEP - No Crank Reference Signal At PCM

Possible Causes
-Faulty Crankshaft Position Sensor (CKP)
-Crankshaft Position Sensor (CKP) harness is open or shorted
-Crankshaft Position Sensor (CKP) circuit poor electrical connection


P1391 JEEP - CMP or CKP Signal Intermittent Condition

Possible Causes
-Faulty Crankshaft Position Sensor (CKP)
-Crankshaft Position Sensor (CKP) harness is open or shorted
-Crankshaft Position Sensor (CKP) circuit poor electrical connection
-Faulty Camshaft Position Sensor (CMP)
-Camshaft Position (CMP) Sensor harness is open or shorted
-Camshaft Position (CMP) Sensor circuit poor electrical connection.

Most auto parts stores sell cheap crappy Chinese made parts, some that even come with a "Lifetime Warranty". These parts are poorly manufactured and/or made from inferior materials. They are often out of specification, or even failed, right out of the box. The ones that are not faulty many times will have a short service life before they fail. Always buy top quality replacement parts and genuine Jeep engine sensors. Numerous threads detail long and frustrating searches for a "problem" that ended up being cured simply with genuine Jeep repair parts.

Cheap parts are cheap for a reason.

I've personally gone through several cheap tps's in the matter of a week before getting one that worked.

Also check the end of the cps, make sure its not coming into contact with the flywheel. Got a great deal on a xj once because the bell housing bolts came loose and ate the sensor.

Quick update, problem ended up being that I had somehow got the distributor off by one gear tooth while installing it (surprised I had it idling at any point that far off).
Also suspected low fuel pressure that I'll be fixing later, but it idles really nicely and runs decently now.