98 XJ, 4.0, AW4, 4X4, 145K miles.

My XJ has developed a couple of issues. It will occasionally hesitate, either on takeoff, while accelerating, or while cruising. It seems to be getting worse, especially at lower speeds. It feels as if the engine loses all power, and if it happens at low speed or on takeoff, sometimes the engine will die. It normally lasts for 1 or 2 seconds, and then runs fine until the next occurrence. Sometimes if I give it more throttle, it resumes running fine immediately.

It also has an occasional slow up shift. At times, under moderate acceleration, engine RPM's will climb upwards of 3000 before shifting.

Both of these issues are fairly new, and I wonder if they are related.

What can cause these issues? I'm suspecting TPS, but really don't know.

Plugs, wires, cap, and rotor have approximately 5,000 miles on them. Check Engine light is on. I have not scanned it.

Thank you for any help.

 

Those code thingies really are awesome. They remove a lot of the stress of guessing.

 

So I've heard.

 

The last CEL I had on my 98 turned out to be caused by a cracked rubber hose on the top of the exhaust manifold.... I believe it was an emissions related problem.

similar symptoms as yours also...

 

Sounds a lot like TPS. There are testing procedures if you search.

 

UPDATE: Codes retrieved, and TPS diagnostics performed.

I scanned and got these codes:
P0420; Catalyst System Efficiency Below Threshold (Bank 2)
P0118; Engine Coolant Temperature Sensor 1 Circuit High
P0123; Throttle/ Pedal Position Sensor/ Switch "A" Circuit High

I did the TPS diagnostics. Power to TPS: 5v. TPS Output ranged from Idle-1.2v, to WOT- 4.2v. Tests performed using an analog meter. Needle swing was smooth through entire range.

It looks to be out of spec according to what I've read. I believe idle voltage should be between .26v and .95v, with WOT voltage of 4.49.

Is this TPS bad?

 

Looks like it.


But it looks like you have other issues as well based on those DTC codes.

 

Thanks for the reply. I have an OEM TPS ordered. I'm going to replace it, clean the IAC and throttle body. I'll see what kind of improvement l get, and address the other issues then.