99 sputters at 2000 RPM

I just picked up a 99 4.0, standard, 231, 8.25.

It's got a odd stutter every time once it hits 2k rpm, regardless of the gear.

While not related, today I gave it new wires, cap, rotor, plugs, and transmission mount.

Any idea what this studder could be?

Fresh tuneup parts that you put in are never a bad idea when symptomatic.

Assuming that you haven't seen a check engine light? If so, pull stored codes for guidance.

My first thought is that you have a bad spot on the "throttle position sensor" When the throttle hits that bad spots, that sensor provides inaccurate data resulting in your symptom specifically at that rpm.

The TPS can be tested with a manual and an analog meter. Easier to find a bad spot with an analog meter than a digital meter. Look for a nice smooth sweep on the meter as you tip in the throttle and go through the entire throttle band. If you hit a bad "spot" while you are watching the meter, replace the TPS.

Good luck and let us know what you find!

The new parts weren't really for the studder, they were for the one code It was throwing, a lean fuel condition. It's gone now.

All I have is digital. I'll give the digital a whirl and if I don't see anything, I'll pick up a analog.

I kind of doubtful it's a TPS, because I would expect it to cut out at the near same throttle position, not exactly 2000 RPM. 2000 rpm is a different throttle position for each gear.

Thanks for the idea though, I'll give it a shot.

Correction: a code is back... haven't had it read yet - will do after I get off work today. Hopefully it sheds some light. Never been happy to see a code before!

Any other ideas?

That code will hopefully yield a clue as to where to look. Post the exact code number here when you have it!

99 4.0 5spd mine has had what I would call a flat spot at 2000 since I bought it last year. At any throttle position any gear when it passes 2k there is a notable....... well flat spot with a good increas in power after 2k. It happens very quick so much so it is almost not there in 4th and 5th gear. I always figured it was a tuning issue do to emission.

My 92 5 Speed had that same problem - feels bogged down but then it kicks back in and takes off? Not sure about that exact RPM level, but it was somewhere therabouts.

It was a weak O2 sensor. It did not throw a code. I see that you have an intermittent lean reading - could be the sensor. Thinks it's lean and puts too much fuel in the mixture. I swapped it out and it was good as new.

I am sure there are threads here on how to test the sensor.

That makes sense that it wouldn't throw a code it would think it was doing its job and and everything was fine after adding fuel I'm going to check mine sensors and I will get back tonight or tomorrow

Thanks guys, I've got a O2 laying around, I'll throw that in and see what happens.

I know this thread is old as shit but did the O2 sensor swap fix the issue? Just ran into this same BS.

None of these threads are as old as any of the XJ's, so the Q&A's are probably still all valid.

Don't know about the posters with the problems, but I can add to my 2 year old comment and say that I had the O2 sensor cause that symptom (lack of power/hesitation passing through the 2K RPM mark) in my 5 speed XJ twice. Once I had a lean code, once I had no code.