Studdering problems

I have a 2001 Jeep XJ 4.0 / Auto/ 4x4

About the start of the year after I took a long trip to texas my XJ started to get a studder in it. My XJ is cut after the cat, "which its a 01 so it has 3 cats", so when it studders it sounds as a little backfire.

The studder only happens on days with temp cooler then 78 degrees.
The studder only happens under heavy throttle.
The studder only happens when the motor is under a heavy load, 50% throttle and low rpms ( 1500-2500).
The studder is not affected by various temps of the motor, such as taking off in the morning from a cold block, or going to stores.

I think it must be a sensor as what determines if it will studder today or not is if its around 80 degrees or hotter outside.

Any clues?

Probably a weak engine sensor.


Test the Coolant Temperature Sensor, the Throttle Position Sensor, the fuel injectors, the fuel pressure the coil rail, and the O2 sensors.

What spark plugs are installed, and how old are they ?

O2 sensors have a normal service life of about 100-150,000. Bucking, stalling and backfiring are symptoms of O2 sensor issues.