01 XJ misfire can't figure it out!

[Drews01xj]

Hello my name is Andrew and i am new to the forum.

I have searched through many post on this forum and google with no luck. (3 months of dealing with this)

2001 Jeep cherokee 4.0 with the auto trans 4x4

I keep getting a misfire code for cylinder 2&5 mostly happens above 3,000rpm. once it throws the check engine light it kills injector pulse to the injectors (2&5) weird thing is i can kill the engine then restart and it will not misfire and run perfectly until taken above 3000 rpm then it will throw the code again and kill the injectors (2&5)

List of things i have done.

New spark plugs (champion)
New Coil
New Crank sensor OEM mopar
New Cam sensor OEM mopar
New Cam sensor body (The distributor like body sensor sits on)
Smoked test no Vacuum leaks
Exhaust back pressure test (passed)
New Ecu
New 4 pintle injectors
6 Brand new injector pigtails
Compression test (passed)
Sea foam/ Fuel system cleaner
Removed entire engine harness and checked for cuts brakes in any wires all is ok
Checked continuity between injectors and ecu pins
New intake air temp sensor
Checked all sensors to verify they are working via snap on scanner (tps,Map etc)

Someone please help im loosing my mind on this one!!

 

[Drews01xj]

Today i checked battery alt and charging system all checked out ok.

Not to sure where to go from here maybe faulty ecu off the shelf?

 

[uglyrenixxj]

Have checked any of the valve train?
Used a vacuum gage on, then ran it up past 3k?
Rocker arms tight?

 

[Unclewolverine]

Check for a slightly rubbed through harness, particularly between the intake and firewall. Thats where i was getting a misfire but only in reverse. Also tps, it will cause all sorts of weird running conditions.

 

[Drews01xj]

I will put a vacuum gauge on it and post my readings

I have removed the entire engine harness removed the wrap and checked the entire harness everything looked good no broken wires or bare wire exposed.

 

[Unclewolverine]

Try checking the tps with an analog multi meter but sounds like you are chasing a ghost in the machine, good luck and I'm sorry. I consider the 00-01 to be the worst of the line because of stupid problems like this that always seem to crop up in them. Chrysler engineers trying to fit 21st century electronics to a 1960s amc.

 

[Tim_MN]

Read this Technical Service Bulletin.


Chysler TSB 0900303
1999-2004 with 4.0 L engine
Multiple Cylinder Misfire due to carbon deposits on exhaust valves.

http://www.wjjeeps.com/tsb/tsb_wj_0900303.pdf

 

[Drews01xj]

I have seen that bulletin I’m just confused on when it misfires and then I shut it off and restart it goes away until taken above 2800 rpm. Does the computer have a misfire counter that it needs to reach a certain number before it throws a code?

I’m ready to put a rebuilt 4.0 in it but don’t want to drop it in and get the same issue that’d be pretty upsetting!

 

[RCP Phx]

Have you tried Seafoam to clean the intake and cylinder head?

 

[Agreen]

I would rule out the base engine as an issue. If it's due to a carbon deposit or improperly sealing valves you would have an issue with it all the time. Just as a precaution, go ahead and do a compression check, but if it passes that then don't waste any more time.
The likely scenario is that you have a wiring issue that is triggered by the harmonic range of that rpm. Since the ECU pulses the ground to the injectors, see if you're still getting +12v to them when it happens.

 

[Tim_MN]

I have seen that bulletin I’m just confused on when it misfires and then I shut it off and restart it goes away until taken above 2800 rpm. Does the computer have a misfire counter that it needs to reach a certain number before it throws a code?

The PCM typically has a counter and it checks sensor data to see if problem X occurs Y amount of times in Z seconds. If Yes, it will trigger the CEL. Turning off the engine usually re-sets the timer.

Does the SnapOn scanner check or adjust the Cam Position synchronization ?



I have never heard of or seen any harmonic wiring problems, that just sounds silly.

 

[Drews01xj]

Yes the cam synchronization was set to 0 degrees

 

[md21722]

I had this problem and it was carbon on the valves. If you have the original head, you are best to just replace the head with a 0331 TUPY or one from Clearwater. It is unlikely to be an electrical/electronic sensor problem, but rather a mechanical problem. Mine did it intermittently between 100-160K. The fix was done at 160K, and it has been fine since. The Jeep now has 408K on it.

 

[Tim_MN]

When the ignition key is first turned ON, 12 volts travels from the ignition switch to the ASD relay. The PCM provides ground to the ASD relay to energize it. The ASD relay sends the 12 volts to the primary side of the coil. If after a few seconds no signal is detected from the CPS, the PCM opens the ASD relay and 12 volts power to the coil and fuel pump is removed.

 

[Drews01xj]

Got a chance to take the valve cover off and run the engine. None of the intake valves are spinning and are heavily scored. Also looks like a few bad lifters or a worn cam since the push rods were spinning extremely fast.