So I'm taking it's fuel injected if it's a 4.0L. Check map sensor, o2 sensor? These can screw with your air/ fuel mixture which can result in leaning out/burning rich, power loss and backfire. 02 sesnor should be replaced every 30k or so anyways. Also if it sounds like it's running on choke you will need to check the AIC(automatic Idle Controller)located on back of throttle body. It could have gummed up which also relates to these problems. You can usually clean AIC by soaking them and scrubbing without replacing. The 02 could be bad and sending false reading to ECU which regulates through AIC adjusting fuel/air mixture. I just went through a similar situation of losing power/cutting out(Surging) in higher gears. Took check fuel pressure, If EFI look along fuel bar on top of engine for a valve cap cover(looks like tire valve cap). Turn key on, take cap off and press valve in and see if gas shoot out. Keep your eyes away or covered. I'm not a mechanic, I just slept in a holiday inn last night!
Last edited by Boanerges; 12-19-2009 at 10:37 AM.