I have a 99 XJ with a 5 spd manual. 170,000 miles on it.

To begin with the jeep seems to lack power, especially compared to my old 93 XJ (with bigger tires).

And sometimes it just seems to bog, or hesitate under acceleration. Almost like it goes lean

Any idea's what might cause this? Or what I can check?


The jeep has got a full tune up including plugs, wires, cap, rotor, and air filter. But none of that seemed to help any

 

No codes stored I assume? Any sign the cat may be partially blocked? Vacuum gauge is handy for that. TPS might cause a lean bog on acceleration.

 

It's got an aftermarket cat on it of some sort. I'd like to remove it all together (we don't require them here), but the check engine light would annoy me.

No codes at all

How can I confirm if the TPS is ok?? Buddy of mine is parting out a low mileage 2001, maybe I should swap the TPS and possibly the map sensor and see what happens?

 

Swapping with a known good part is a good test.
Otherwise you measure the TPS output voltage (center wire) with the key on, engine off. Slowly open the throttle while watching the voltage. Should rise smoothly with no skips from <1V with the throttle closed, to just under 5V with it wide open.
I'd at least test the cat to make sure it isn't creating an obstruction. Vacuum gauge works, or drill a small hole before and after & do differential pressure test. Or just yank it off temporarily and see if it runs better.

 

CRUISER’S VACUUM TEST FOR EXHAUST RESTRICTION
Your vacuum gauge should come with an instruction booklet outlining the procedure. Hook the vacuum gauge up to a source on the intake manifold. Start the engine and note the vacuum reading. Usually 17 to 21 inches of vacuum. Throttle the engine up to 2,000 to 2,500 RPM for 20 seconds or so and the vacuum reading should stabilize to the same reading you got at idle. Let the throttle snap shut. The vacuum reading should shoot up about 5 inches of vacuum higher for a second and then come quickly down to the original reading. If the vacuum reading stays high and comes down slowly with jerky needle movements, you have an exhaust restriction.