Miss at or near 2500 rpm

[BAs96XJ]

I have searched for the last 30 minutes with no success so here it goes.

I have a 96 XJ, 4.0, AX15 with 153k. I just replaced the TPS. The 2 O2 sensors are less than a year old. Brand new exhaust from head pipe back. I have just recently ran some seafoam thru it. I have a miss in 4th gear at 2500 RPM. I can't duplicate it in any other gear yet. Usually it is under acceleration. Any ideas. Most tune up stuff has less than 15 k on them.

BA

[jeepsrock]

I would start with the usualy things.
1. spark plugs and wires
2. cap and rotor.
3. Check map sensor
4. check distributor for play

pete

[8Mud]

If it´s bucking or that kind of hard miss at 2500, that is usually an indication of a lean burn. Your running out of fuel or pulling to much air. It usually shows up again, at or near top end or at or above 3500 RP M's and often won't accelerate to (or near) red line, while in a low vacuum (under load/throttle open).
How is your idle? Idle can be an indication of a vacuum leak or a poorly functioning O2 sensor.
If it starts missing at mid RP M's and gets worse as the RP M's get higher and eventually feels like the valves are floating. It is often a sign the spark is breaking down. Which can be anything from moisture, a corroded cap, to bad or loose coil and plug wires.
Are you geting any trouble codes?
Distributor caps seem to wear out twice as fast as plugs for me. They get corrosion on the high voltage lugs and the inside covered in carbon dust.
I've seen a bunch of XJ's where the rear O2 sensor wires were cooking on the exhaust. It sometimes throws a code, sometimes not. But it sure can't be good.

[BAs96XJ]

Good info. No codes have shown up. I will check the dist cap tomorrow. It seems to pull all the way to the redline so a lean situation probably is not the case. I will do some investigating in the morning. The idle was running high until I changed the TPS. Now it idles normal and smooth.


BA

[old_man]

Did you adjust the TPS?

[BAs96XJ]

How do you do that? I thought it was plug and play.

BA

[old_man]

Bingo. Do a search on TPS and adjust.

[BAs96XJ]

Would my Haynes manual tell how to adjust it? I have been searching since your post.

BA

[Dr. Dyno]

Bingo. Do a search on TPS and adjust.

The TPS is non-adjustable on '91+ HO models; only on Renix.