ive been trying to fix this problem with no luck, I fire my jeep up and it runs fine, after about 3 mins rpms start to die down but it catches its self before the motor complety dies, this last for about 1 minute. when in drive and it does this it loses power and will not accelerate. seems like when i come to a stop light and have to mash the brakes the rpms go down to about 200 somtimes, and other times it is fine.

any ideas to this? thanks

 

need a tune up?
fuel pump/filter?
TPS/MAP?

I would start with replacing everything in the ignition department because its something that needs to be done anyway (i gained a couple MPGs doing mine)

I would also replace the filter cause thats easy if u gotta old xj.

TPS&MAP can be checked with a multimeter, never did it, but maybe someone nice will tell you the results you should be getting during testing

 

Year/engine?

 

1998 4.0, i bought a new before the cat 02 sensor today, im going to install it tomorrow sometime, and im thinking to test the tps to see if it is bad, but if those 2 things check out and the problem is still there im stumped. ive replace the tcm, nss had a code for it, and none has help so far. im thinking it might be the tps from reading on here. hopefully it will be then i can be done with this problem.

 

Post ALL existing codes here for comment.

Ensure ALL tuneup hardware is fresh. Champion copper plugs gapped to .035, new wires, distributor cap, rotor.

Testing your TPS makes good sense here. You'll need a manual and a meter (analog best)

As well as testing your fuel pressure on the schrader valve on the fuel rail. Must use a gauge. For a 98, you're looking for 49.2 psi, plus or minus 5 psi.

Fuel delivery is something that needs to be ruled in or out early in the troubleshooting process.

 

I was gonna lean heavy on the 02 sensors, but I'm feeling FPR.