Backfiring in closed loop/ warm - JeepForum.com
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post #1 of 3 Old 06-14-2021, 10:31 AM Thread Starter
Jackknutson
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Backfiring in closed loop/ warm

So I’ve got a 2002 wj 4.0l. Runs good I. Open loop when cold but when it goes into closed loop and warms up it backfires and stutters and sometimes dies. Usually only backfires and stutters when I’m heavy on the throttle so if I drive it carefully I can keep it running. Replaced almost everything in the book. Fuel injectors, battery, alternator, pcm, coil pack, passenger side wiring harness, NTK O2 sensors, crank and cam position sensors, fuel regulator/filter, spark plugs, coolant temp sensor, thermostat, fuel pump relay. It’s not throwing any codes. The guy who had the Jeep before me didn’t seem to be the smartest (lots of loose bolts everywhere) Currently in the middle of fixing a vacuum leak at the intake/exhaust manifold but I don’t think that’s my problem. Let me know what you guys think, thanks

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post #2 of 3 Old 06-17-2021, 02:49 PM
laybackman
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Originally Posted by Jackknutson View Post
So Iíve got a 2002 wj 4.0l. Runs good I. Open loop when cold but when it goes into closed loop and warms up it backfires and stutters and sometimes dies. Usually only backfires and stutters when Iím heavy on the throttle so if I drive it carefully I can keep it running. Replaced almost everything in the book. Fuel injectors, battery, alternator, pcm, coil pack, passenger side wiring harness, NTK O2 sensors, crank and cam position sensors, fuel regulator/filter, spark plugs, coolant temp sensor, thermostat, fuel pump relay. Itís not throwing any codes. The guy who had the Jeep before me didnít seem to be the smartest (lots of loose bolts everywhere) Currently in the middle of fixing a vacuum leak at the intake/exhaust manifold but I donít think thatís my problem. Let me know what you guys think, thanks
What about the Throttle Position Sensor (TPS) in the throttle body? It, and the bore it sits in can get really dirty. Is it throwing any trouble codes?

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post #3 of 3 Old 06-23-2021, 12:09 AM Thread Starter
Jackknutson
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There were no codes. Found the problem though. Crank position sensor wire was stretched tight and at an angle to a bracket causing it to short to ground
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