What sensors should I look into?

[jedo1507r]

The 4.0 I6 surges sporadically in power and hesitates when throttle opens. I have replaced the MAP sensor, Oxygen sensor, and actually have cleaned the intake manifold (just because I have the time). I was thinking of replacing the EGR valve assembly but doubt it. Any suggestions?

(XJ in question: 1989 Jeep Cherokee Ltd.)

[8Mud]

When my EGR was acting up, it would occasionally stall at low speed (usually right in the middel of a 90 degreee turn, interesting) and would idle really rough. Hardly noticed it was bad above 1000 RPM or so, though it did occasionally act up during deceleration.
Have you done a TPS adjustment, the TCU half of the TPS is the side actually adjsuted, but the other half is the throttle position inputs for the ECU. I had a flat spot in the ECU half of my TPS, that would cause a hestation at a certain throttle position (about 1/3 throttle).
I usually start by doing a fuel pressure test, when troubleshooting surges and bucks. Fuel filter replacement.
Then the O2 sensor (you've done that but it's possible the O2 sensor problem may be in the wiring, connector or heater relay). Check the O2 sensor heater circuit (relay and wiring). The O2 harness in the Renix (continues from the front of the injector harness down the front of the motor) has often been known to cook on the exhaust manifold behind the power steering pump (hard to see). Especially after an intake manifold removal and then rerouted by accident so it runs very near the exhaust manifold.
A sticky IAC can cause problems. But usually causes more symptoms. Like stalling at idle, high idle and hesitation (too lean) when quickly opening the throttle.
Best guess would be the TPS, which will mess with your timing causing hestation, flat spots in the throttle and other problems.
My CPS is getting flacky, my rear main is leaking again and the CPS is covered in oil. The motor occasionally surges or gets a light buck at highway speeds and occasionally has really poor throttle responce off idle (it barely accelerates). It seems to be an intermitant thing (only happens occasionally) it sometime refuses to start. I'll have to see what happens first, the CPS craps out completely or I fix my rear seal leak and put in the new CPS (laying in my tool box).

[jedo1507r]

Thanks for your reply.

I think I'll try your suggestion of the TPS, since there are flat spots when playing with the throttle. The fuel pressure test registered at 34 p.s.i. (it actually ran at 8 p.s.i. before I realized the fuel pump had a loose hose), but The O2 and MAP sensors weren't sending the correct voltage on the diagnostics machine, but have shown improvement after.

But about the bucking, it had plenty of those while using that diagnostics machine, popped like a popcorn popper. The exhaust was too rich, I guess.

[bcmaxx]

I have intermittent poor performance,very poor fuel economy, rough and loping idle and popping and farting (power cuts in and out) especially on decel at highway speeds. heres what I replaced. Injectors,fuel pump,fuerl filter,oxygen sensor,engine coolant temp sensor, intake air sensor, cleaned IAC,Cap, rotor, plugs, Map sensor,diabled egr. Problem still persists.Our Jeep dealer does not hve the proper equiptment to diagnose (Off-board codes), therefore I am playing the sensor replacing game in hopes of fixing it before I go broke, will try tps next.

[Rocketman]

Fuel Pressure Regulator. Just because the test shows a decent pressure doesnt mean it isn't leaking. It can cause big time issue yet "bench test" fine.

[1985xjlaredo]

bcmaxx (http://www.naxja.org/forum/member.php?u=16373) I would have replaced the TPS first in fact that is what i did.
But I still have the problem it is just bucking at about 1/4 throttle at 45-65MPH

[jedo1507r]

How about the catalytic converter? A buddy of mine told me about the possibility of it being clogged (since it's been ten years since there was a new one).

As far as mine, I've driven it through a couple of embarrassing miles, couldn't go above 30 MPH and have a back seat full of smoke, ha. So I could look into that. TPS and Fuel Reg. have been changed with slightly better success. Still "farting" away though - people had to duck when I came by!

[jedo1507r]

So the Jeep is running as it did, the catalytic converter had a hole blown out of it and the muffler had bursted, ha. Everything runs, but it wants to stall within the first few minutes. Any ideas?

[1985xjlaredo]

Intake air sensor? Did you replaace it? That could be the problem if its only doing it when its cold?

[jedo1507r]

Yep, that was part of the problem. I just have to warm the engine enough (three minutes or more) to make it run smoothly and not have sudden stalls.