XJ insainity

[youdidwhat]

Ok so I just joined, but I have been a member of KCJEEPCLUB for 7 months now and I have stumped quite a few with this question.

Let me set this up, then the question.

I was rolling down the hwy doing normal hwy speeds when out of the clear blue my 98 XJ starts loosing power, then it surges back to normal rpm then cuts out again, I pull over and its running real rough, coughing sputtering, and sitting at about 300 rpm. I attempted to rev the engine and it did nothing. again I attempted to rev the engine, then it died, it started back up but is still running rough, then some times it surge to normal rpm and drop off again. this behavior is coupled with a real weird surge that happens at about 3500 rpm that feels just like I'm hitting the gas then letting up straight away over and over.
most of these symptoms are nonexesistant when the XJ is cold or just started but once I get to operating temp. it starts again.

so my question is.

DOES any one know what is wrong with my rig, or has had this problem in the past.

any help would be great!

one more thing, intrestingly enough there are two of us in the club having the same problem with 98 XJ's that started at the same time.

[Lifted79CJ7]

Clogged catalytic converters? I know 97 TJ's had that problem I think. If you can't get your exhaust gas out, then you can't pull more air in - resulting in a dead engine. Just a guess.....

Jack

[youdidwhat]

checked that,

plenty of flow.

we are looking more at the TPS or a computer control modual.

[Mudrat]

Or a vacuum that's open at temp .. ?

[Soylent_Green]

bad O2 sensors will give that effect. I had exactly the same symptoms in my bronco.

(Your rig's computer will ignore the O2 sensors until it reaches operating temperature, until then the computer will run a closed loop that will "fake" a reading that it will use to run lean and warm the engine up.)

[Soylent_Green]

Well, come to think of it, a faulty fuel pressure regulator may be the cause. sometimes they go bad in a way that they will ony not work when they get hot.



Another possibility is an Idle Air Control valve. but that's usually just a mid-90's ford problem.

[Soylent_Green]

Ah, never mind, I'd bet on the O2 sensor.



Too much ~~~~~~~>

[youdidwhat]

would either of those send code to the computer, because I took it out yesterday with a hand held attached to the computer and got it to act up but got no codes from it.

Ohh and the TPS cleaning did not help

I think my troble is too much and not enough

[Soylent_Green]

Hmmmmm......no codes.

Well, that really throws a wrench into it.

[pyagid]

LIke the others said, I would Check the Fuel injectors, Make sure none are leaking, or clogged, Maybe Change the fuel filter, if that is partially clogged it could be starving for fuel at the higher RPM, also check your plugs, wires, cap, rotor, and air filter.

All of the tune up components could cause these symptoms. I think someone on another board just had a similiar problem if i could find the link i will post it here

-Paul