So my problems mysteriously come and go with my 98' XJ. 4.0, auto, 129k on the clock.

My problems are back with vengence and now the truck doesn't even run. Fires up after priming the key 4-5 times, misses, backfires, will idle at 200-300 rpm for about 30 seconds before dying.

Changed out the TPS for an Advanced Auto parts one and it hasn't fixed the issue. Fuel pressure is still 43-50psi. I'm beginning to run out of patience and funds on this truck.

Only CEL codes I saw was a P0123 and P0141. Neither have come back since I replaced the TPS and reset the battery.

This is how it was acting before I replaced the TPS and reset the battery. Now it won't even rev past 1k and idles way low and is missing its *** off.





Thoughts, Opinions?

 

I wanna say either Crank or Cam position sensor.

 

The Crank Position Sensor was replaced with an OEM sensor probably 3-4 months ago. Do they go out that quick?

 

Unless it was defective, no. Try the Cam sensor then i guess.

 

I have the same problem currently.. doing more checks tomorrow.
Try checking the vacuum at idle and see if/how it fluctuates

 

These $100+ sensors will be the death of me...

Thinking about getting them from the junkyard or off XJ's being parted out on CL.

x91evo, I saw your thread, and we do have very similar problems. Check all your fuses, I had a blown mini for the o2 heater circuit thatr was causing similar issues.

 

If you get them at a junkyard grab a few if you can, just in case the first one was defective.

 

That's the worst part of getting used parts. No clue if they're good or not. There's a few yards locally that have some cherokee's so I'll be sure to get as many parts that can potentially fix mine as possible lol.

 

Yeah, i usualy take a mutlimeter with me, but IDK if that will help with finding if a sensor is good or bad. And go ahead and pocket a few hand fulls of fuses while you're there lol, most yards don't care about fuses.

 

LOL I grab fuses and relays everytime I go. Always good to have those in the rig. I tried testing a couple of my sensors on the truck, but wasn't able to hold everything by myself, needed a third hand. Any easy way of testing them on your own?

 

a third hand? lol i thought all you had to do to check a sensor for proper function was if ohms were in spec for the sensor?

 

I guess I read wrong, where you had to tap the pins or wires at the harness plug to check if everything was operating correctly?

And for the TPS you have to do all that while pening and closing the throttle slowly. Is all that possible with just 2 hands?

 

Im not sure about the CPS
oh didnt think about that
alligator clips? haha

 

Made a trip to the local junkyard and found a really nice 99 Sport. Should have pulled some more of the more sought after parts, but I'm determined to get mine fixed first.

Pulled the whole throttle body, map sensor, iac valve, and tps off the 99 in the yard. Also grabbed an intake temp sensor that bots on the intake manifold, along with a cam position sensor.

Replaced:

-entire throttle body
-map sensor
-tps
-iac valve
-cam position sensor
-new accel distributor cap
-accel rotor

Also checked the plugs while I was at it. They were a bit black from misfiring and running rich, but cleaned up and looked good.

While replacing the parts, I disconnected the battery so the ECU would reset and hopefully cure my problem, but that wasn't the case. It's still acting just as bad as before.

The only other parts I haven't replaced RECENTLY(last 2 weeks) is the coil and crank position sensor, which were both replaced 3-4 months ago. I'm seriously lost on what else to do or look for. I guess my next step is to pull all the OEM wire loom and start checking for bad/faulty wiring.

Made another low quality video of how it's running, or attempting to run now.

 

Trust me, if you see a part you want and have the money, GET IT. I had my chance to get an OEM tire carrier, blew it because i wanted to make sure i could get a full size spare first.