My Cherokee has the 4.0 fuel ing. engine. when you start up, it will run on a fast idle for a while, then act like it is running out of gas and starts chugging. When you pull out and accelerate to shift, the engine seems to "buck" and "jump" and sounds hard on drive train. I've flushed gum-out in the carb, and cleaned whatever I could take apart on the carb, and this still didnt help. Any suggestions are welcome.

 

Just throwing this out there to cross off the list... how is the water pump? I didn't have a cold engine problem, but semi-warm it would really have a BAD idle that sounds similar to what you have. Whole car was bucking one time, until it warmed up again.

Cold fine, hot fine, but short trips that were in and out (like getting coffee) it was terrible.

I had actually heard the water pump failing, but didn't know what the noise was. (something like a scraping a metal bowl on concrete) It actually ran fine for 3-4 months until it dumped all the coolant from the radiator (but not the tank)

Just a thought, since bad water pumps seem to cause bad idle on a lot of cars, as I discovered after trying to figure out my ZJ's problem.

 

Has new water pump already installed. Someone suggested a throttle body sensor control could be acting up. I'm going to look into that. I'll let ya know if that works!