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Chris
Chris, Shop Foreman
Category: Jeep
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Experience:  Jeep Certified Master Tech
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My 2001 Jeep Cherokee Sport 4.0L continually gets a cylinder

Customer Question

My 2001 Jeep Cherokee Sport 4.0L continually gets a cylinder 1 misfire. It also, after driving on the highway at high speed and then coming into city traffic, starts misfiring and check engine light starts flashing. If I shut it off and restart it stops missing but sometimes comes back several times. It only does this after I have been driving highway speed and then return to city driving. I have changed coil park, plugs, injectors, all sensors except camshaft position, had head rebuilt. What gives?
JA: Does the light stay on, or does it blink?
Customer: It stays on when I get the cyling
JA: Are you fixing your Cherokee yourself? What have you tried so far?
Customer: It stays on when I get the cylinder 1 misfire, but flashes after running at highway speed and then going to city traffic.
JA: Anything else you want the mechanic to know before I connect you?
Customer: That's pretty much it.
Submitted: 6 months ago.
Category: Jeep
Expert:  Chad Farhat replied 6 months ago.

Hi, I'm Chad. Welcome to JustAnswer. I'm reviewing your question and I will be posting your reply ASAP.

Expert:  Chad Farhat replied 6 months ago.

hey how are you

1- so coil , injectors plugs brand new correct ?

2- have you replaced the intake manifold gasket when heads was rebuild ?

3- have you checked for vacuum leaks

4- fuel pressure checked : are you seeing 49.2 +/- 5 PSI

5- If the PCM getting hot and at that time intermittently kill injector #1 , that could be the issue ( A rebuild one will be way to go if that is the issue )

allcomputerresources.com will be good site , it will be plug & play no programming needed

is this the original PCM of the Jeep ?

Please let me know

Thank You

Chad Farhat

ASE Certified Technician

Expert:  Chad Farhat replied 6 months ago.

https://www.dropbox.com/s/90vckoqoz6z0vay/File%20Oct%2011%2C%203%2055%2030%20PM.png?dl=0

This the The wiring circuit diagram

a cam sensors also will cause this ,also connected to PCM

Chad

Customer: replied 6 months ago.
All gaskets were changed when head was redone. Also it has a rebuilt PCM. I changed the camshaft sensor top, but not the shaft. I saw where it could be camshaft sensor, timing chain. Also heard a couple comments about the clockspring affecting the TPS which gives the PCM bad reading.
Expert:  Chad Farhat replied 6 months ago.

yes on all the above

wish i had a specific answer , let me ask you this , does it reset when you cycle the switch

Expert:  Chad Farhat replied 6 months ago.

has the problem been consistent always does it after all replaced or somethings made it better as far as it takes longer to throw the check engine light

after a certain repair you did , or that work done at once

Customer: replied 6 months ago.
I had these things done over time. The issue seems to come back as soon as I drive on highway for a period of time and than into city traffic.
Customer: replied 6 months ago.
Also replaced fuel pump.
Expert:  Chad Farhat replied 6 months ago.

so all that time and parts replacement that misfire problem stayed after highway use ?

Customer: replied 6 months ago.
for awhile now.
Customer: replied 6 months ago.
I believe the misfire problem started before they diagnosed the head issue. Had the engine overheat a couple of times, which damaged a couple of valve seats. Had the head rebuilt. The valve seats weren't on cylinder one though.
Expert:  Cary York replied 6 months ago.

Hi, I’m Cary and I’ll be helping you today.
Please understand that I can't smell, hear, or touch the vehicle, so patience is appreciated. Before leaving the site make sure and leave me a rating. You can still reply to me as many times as needed, even after the rating..

I have seen this on a 4.0L jeep before. It is defiantly a valve train problem. Since the head has been worked I would have to question the hyd lifters. Are they original?

Expert:  Cary York replied 6 months ago.

You may have a lifter on #1 pumping up at higher RPM and speeds and when you stop it is holding the valve open to long and opening to far.

Expert:  Cary York replied 6 months ago.

I do have a suggestion but it is not exactly a text book repair.

Customer: replied 6 months ago.
I'll have to check with mechanic about which valve stems were replaced. If you replace one, shouldn't they all be replaced?
Customer: replied 6 months ago.
What's your idea?
Customer: replied 6 months ago.
I had a couple of feeds talking about the clockspring causing an ossue with TPS communication with PCM. Have you heard this before?
Expert:  Cary York replied 6 months ago.

There is a service bulletin about the valve springs. I have replaced valve springs to fix similar problems on the 4.0L. But the head has been worked so the should have check valve spring pressure.

Expert:  Cary York replied 6 months ago.

No never heard of loss of communication.

Customer: replied 6 months ago.
Would a worn timing chain and/or camshaft sensor cause it? I replaced the electical top end of the sensor, but not the bottom end.
Expert:  Cary York replied 6 months ago.

No not a timing chain.