Have the 4.0L I6 engine. For the past several months the RPM's would climb to about 1200 or 1300 at idle, in park. Didn't happen all the time. Two weeks ago we were driving on the highway, and I would notice under acceleration up hills or passing a slight dip in engine power, almost like the transmission was slipping. Took it to the shop, computer had no codes, tranny ok. One spark plug had carbon build up, so they did a tune up and cleaned some of the throttle plates. Ran great for about 30 minutes, then driving down the highway, and the jeep starts bucking back and forth like the engine would die, then refire. Pulled off highway to a stop light where it bucked again then died. Restarted the engine, pressed the accerlator but the jeep wouldn't move and the rpm gauge showed about 200. Floored the accelerator with no luck. RPM's around 200, barely creeped into a parking lot. Waiting 5 minutes, fired right up and drove like normal back to the shop.

No error codes again in the computer. Tech did get it to die for him once after driving it about 3 times in one day. Hooked it up to the gauges at the shop but couldn't find anything wrong.

Could it be a TPS sensor? I mentioned it to him, but he said it looked fine on the oscilliscope, so did checking out the fuel filter.

Have the 4.0L I6 engine. For the past several months the RPM's would climb to about 1200 or 1300 at idle, in park. Didn't happen all the time. Two weeks ago we were driving on the highway, and I would notice under acceleration up hills or passing a slight dip in engine power, almost like the transmission was slipping. Took it to the shop, computer had no codes, tranny ok. One spark plug had carbon build up, so they did a tune up and cleaned some of the throttle plates. Ran great for about 30 minutes, then driving down the highway, and the jeep starts bucking back and forth like the engine would die, then refire. Pulled off highway to a stop light where it bucked again then died. Restarted the engine, pressed the accerlator but the jeep wouldn't move and the rpm gauge showed about 200. Floored the accelerator with no luck. RPM's around 200, barely creeped into a parking lot. Waiting 5 minutes, fired right up and drove like normal back to the shop.

No error codes again in the computer. Tech did get it to die for him once after driving it about 3 times in one day. Hooked it up to the gauges at the shop but couldn't find anything wrong.

Could it be a TPS sensor? I mentioned it to him, but he said it looked fine on the oscilliscope, so did checking out the fuel filter.
HI COULD BE THE TPS. SENSOR FIRST CHECK THE CATALYTIC CONVERTOR STARTING TO GO OUT HOPE THIS HELPS DALE
jeepman600@aol.com :smokin: