Jeep backfires?

The very common cause of this problem on your Jeeps engine is the crank sensor,it sends a signal to the computer showing the engine is spinning,when this signal drops out the engine will shut down. It is located on the back of the engine at the bellhousing. See the image of the sensor,and another showing how it is mounted. It is accessed from under the vehicle.

Also check the ignition wires are routed correctly and connected properly to the plugs.And not got dirty/worn out or loose.

It can be faulty valve springs. Valve springs when get weak, they won't close the valves quick enough and  backfiring is noticed. The only way to check them is to take them out and check each one. You could narrow it down by getting it to back fire and pull plug wires until the backfiring stops. That will tell you which cylinder has the problem.So you can continue replacing that cylinder.

This possibilities will help.
Thanks.

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