2.5 4 cyl engine hesitation
I have a 1997 TJ with a 2.5 4 cyl engine, approx. 67k miles, 5 speed manual trans & a/c. My problem is that 75% of the time it will hesitate/ stumble when I first take off. Warming it up is not an issue. The problem occurs whether I warm it up for 10 seconds or 10 minutes. The hesitation does not occur in reverse, I back the Jeep out of the garage without a problem, but as soon as I put it in 1st gear and try to drive away it drops to approx. 100 rpm's and will not rev up. It does not respond even if the throttle is released. The only cure is to push in the clutch and release the throttle and wait for it to "clear" the problem which will take 5-10 seconds. Once the problem has occured it will not happen again until the engine is turned off & then restarted.
This has occurred since the Jeep had 15k miles on it. After numerous warranty repairs Jeep was never able to find the problem. The repairs that have been done include a new exhaust manifold due to TSB from Jeep, new plugs and wires, new computer downloads from Jeep, throttle body clean outs, new fuel injector rail & I even put a K&N FIPK air cleaner system on it. Other than this problem the engine runs great.
I live in the Phoenix, Arizona area if this tells you anything about altitude and weather conditions pertaining to the engine air/fuel mixture. The time of year does not make any difference either. I have done a search and found nothing.
Any one else have a similiar experience? Anyone have any ideas on how to solve this?
Thanks for any help!