Tom Moses

Hello all,

I have a 99 XJ limited with the 4.0 6cyl w/ automatic trans. Started stalling pulling away from stops, and when warm wouldn't want to start again. Check engine light, but no code when scanner is connected. Intermittent rough Idle, loss of power and bogs when put in gear. Thought it was IAC, cleaned it along with throttle body and tested. Worked fine and power was back until it got warm, replaced IAC and same problem. Fuel pump is priming like normal, exhaust shows signs of running rich. O2 sensors are a year old. Next guess is to replace plugs, wire, cap and rotor. Am I on the right track or am I chasing my tail.

Any suggestions would be greatly appreciated.

Thanks,
T

XJ_XJ

How long has this been happening? How many miles have you drive since you started have this problem. Did the jeep sit for a while?

Roler

Finish the tune up
clean up your grounds

I'd say likely CPS or CAM sensor after that.

truchas

Google MAP sensor. Don't buy one from the dealer, they will rip you off big time.

truchas

Tom Moses

Alright, finished the tune up, and cleaned the maf sensor. Check engine light on still no code. What is happening now is it starts, and idles like normal and revs in park like it should. After a 5-10 minutes of idling at about 700rpm, it jumps up to about 1000rpm and when you rev it, it stalls. Let off the gas before it stalls it revs to about 2000rpm then back down to 1000rpm. If it stalls you have to wait about 10 minutes before it will start again. Any ideas?

Roler

Yes, see my post #3...
CPS is very common to fail at some stage. Given your idea if running rich, CAM sensor. When faulty they can give similar symptoms.

Your symptoms are very common and I bet if you search, you are going to find numerous threads on it. And at least half will be about the CPS.

Tom Moses

Alright, I will try the CPS tomorrow. looking at parts stores online there doesn't seem to be a CAM sensor for my vehicle.

Roler

Get a OEM/Mopar one If still available
All those threads with CPS problems will also advice you to go with that, and not the cheap ones
Saves headaches down the road.

There should be a CAM sensor for your year.
​​​​​​
They are also called Distributor pickup coil
copy/paste this link (can't link it) or look on Rockauto etc.

https://www.rockauto.com/en/catalog/jeep,1999,cherokee,4.0l+l6,1431776,ignition,distri butor+pickup+coil,717

Tom Moses

Which would you try first, the CPS or the pickup coil?

Roler

Good question
- CPS due to it failing more often than CAM
- CAM because you state exhaust gives idea of running rich.

I changed CPS which solved the issue.
When similar symptoms occured months later, it then also had exhaust smelling like fuel with it. New CAM solved it on that occasion. Been fine ever since.

( CAM sensor is relatively cheap)

Tom Moses

Alright, then I'm going to try the cam sensor first and go from there! Thanks, I'll update after.

BlueRidgeMark

Check for vacuum leaks before spending any money on parts. Also check the O2 sensor fuse and wiring.

Tom Moses

Alright, update.

I have replaced both cam and cps. And it is still idling for about 5 minutes like normal, then goes into high idle where it stalls when you touch the gas. Bright side it no longer smells like it is running ritch anymore. Any ideas?

juan3047

BlueRidgeMark is spot on. I had a similar problem. Looking at MAP I noticed a vacuum line was out from intake manifold. The rubber 90 was split. Autozone had one that I had to shorten. Replaced it and Jeepie runs much better with original MAP back. Hopefully fixed.

juan3047

BlueRidgeMark is spot on. I had a similar problem. Looking at MAP I noticed a vacuum line was out from intake manifold. The rubber 90 was split. Autozone had one that I had to shorten. Replaced it and Jeepie runs much better with original MAP back. Hopefully fixed.