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Starts when cold, starts when warm, but not inbetween

M

Muddy-93

NAXJA Forum User
Location
Norway
I'm going crazy here! My Jeep (-94 XJ 4litre HO) has developed a strange problem. When the engine is cold, and hasn't been driven for a while, it starts and runs just fine. If I let it run until it's nice and warm before I stop it, it will start up again just fine. But if I start it cold, let it run for a couple of minutes and stop it, it won't start. No matter how long I try, it's dead. Then I wait for a couple of hours, and WOILA! it starts again. What can cause this? Please help me :helpme:
 
A hair drier can really help in finding the problem.
Preheat an area or part then try a start.
Slow going, but better than guesses ($$$).
Allow for time for the heat to soak in.
-------

Also might try unplug/replug the crank sensor a few times as they can get iffy. Quick easy test.

Good Luck,
Orange
 
Hair drier and coolingspray is something I've used alot when troubleshooting electronics. Never thought of using it on my car. Good idea. As for the CPS it was replaced last summer, so it should be OK. I have also replaced the TPS, and cleaned out the throttlebody along with the IAC and IAT. I've ordered new IAT and oxygensensor, so they will be replaced soon.
 
" But if I start it cold, let it run for a couple of minutes and stop it, it won't start. No matter how long I try, it's dead. Then I wait for a couple of hours, and WOILA! it starts again."

This is what stood out to me..........

If the camshaft position sensor signal is lost while the engine is running, the ECU will calculate spark timing based on the last cam signal and the engine will continue to run. However, the engine will NOT run after it is shut off.

Because of the way the cam sensor works and the symptoms you describe, I would absolutely test the cam sensor when symptomatic. Located inside of the distributor.
 
Muddy-93 said:
How can I check cam sensor?
Click to expand...

Get a manual. You'll need one in the future anyways. Best money anyone can spend that works on their XJ.

FSM (factory service manual) is the best. Chiltons/Haynes are generic and can have a few errors.

Any manual though should have the procedure. You'll need a multimeter as well.
 
The o2 is out of the picture till closed loop kicks in, so go for the basics first.

Agree that the Cam sensor is a good start- warm that area up, try a start. If that is the problem area it will act different.

Crank sensor next- (A brand new part can go bad-- test it)
PCM-
etc.
----------
Go for THE MOPAR FSM, -ONLY-! ---be sure its for your exact year.---

FSM, a multimeter, and code scanner are just about must have tools, but they pay for themselves after a few repairs. Plus save a lot of time.
 
Last edited:
I have both Haynes and FSM from GreatLakes, so I guess its time to start reading. Can I use my digital Fluke multimeter when testing the camshaft sensor?
 
The o2 is out of the picture till closed loop kicks in, so go for the basics first.

Agree that the Cam sensor is a good start- warm that area up, try a start. If that is the problem area it will act different.

Crank sensor next-
PCM-
etc.
 
Been out driving today, and the Jeep is running fine. As long as the engine is warm, there is no problem. The engine is purring like a kitten, and my rig is performing good. I'm going to wait for the parts I've ordered before I do some more work. After I've changed the IAT and O2 sensor, I am going to check the Cam shaft sensor. The parts I've ordered includes the CCV hoses, to eliminate vacuum leaks. Hopefully this will fix my problems.
 
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