Im not much of a mechanic but i know the basics. However my 89 jeep cherokee (automatic) has been letting me down. the rpms jump up and down (not too much) noticeably. And it stalls out every once in awhile if i dont give it gas or i stop. Also when im driving it feels like its trying to go and will bump alot then it will take off. Anyone know what the problems could be? please help me. 4.0 liter 4x4

 

mileage?

Also explain what you mean by "bumps alot then will take off"?
Give a more detailed description, is there a sound thats associated with the "bumps"?

 

150k miles, and Like when i press the pedal down it will push like its speeding up then stop and push again but really fast. its hard to explain, and its does make a knocking sound but that happens when the rpms are high

 

Trying to diagnose something like this over the 'net is kind of hard, but I would do a good tune-up with quality parts. Clean the throttle body. If the problem persists, test the fuel pressure.

 

May want to look into a Throttle Positioning Sensor (TPS) at the parts store. Should be about 35.00 at Napa. DON'T GO TO AUTOZONE FOR THIS!!! i learned my lesson the hard way. But i would also get a new throttle body gasket and a can of carb cleaner. Take a toothbrush and about 20 mins to clean out the TB really well. There is also a ICA on the passenger side of the TB. take that out and clean the part and its home out really well. Not a har job at all but will help with throttle response. Here is a link on the "How to"

http://www.xjtalk.com/showthread.php?t=10844