I recently purchased a 2001 sport-to replace my high milage 2001 sport. Both have the 4.0 with auto. all pretty standard. my older jeep (225k miles) has so much more get up and go - I can hardly tap the gas and the vehicle lunges. the lower milage jeep feels like I'm towing my boat. Gas milage: 17-18 (high milage) v.s. 14 (lower milage). I've checked the joints nothing seems to be dragging, throttle body / top engine clean, air cleaner - all the usual suspects check out ok. Any thoughts?

 

did you do a compression test? replace injectors? first things I thought of.

 

Run some seafoam through the gas tank

 

No to all. Any idea what the compression should be? Thanks

 

Brake caliper(s) sticking, I have seen the parking brake hang up. Does the engine rev up in park without hesitation?

 

Try the upstream O2 sensor. They can go bad without throwing a code

 

I think compression new is 140-150. been awhile since I looked that up. mine with 140k is about 120-130.

 

Basics first. I saw no mention of spark plugs. Get fresh ones in there. For the 00-01 with the distributerless ignition, I recommend NGK Coppers gapped to .035.

Yes, oxygen sensors can get "lazy" before they get to a point where they set a code. Replacing at least the "upstream" ones (especially if they are originals) would be something to consider as they have an expected lifespan of between 100k and 150k, depending on efficiency of the engine.

Compression spec. for the Jeep 4.0 engine is 120-150 psi, with no more than a 30 psi variation between cylinders.