P1391 Fault and new sensors did not fix

[crowjc]

I have a 2001 TJ with a 4.0. The engine runs rough, has loss of power, shutter, and the tachometer jumps up intermittently. On a scanner I see the tach jump from 750 to 1400 or more for an just and instant. The engine misfires and studders. It has a P1391 code for intermittent loss of CMP or CKP. I replaced both the cam position sensor and the crank position sensor and it had no affect. I also tested the harness from the ECU to the crank position sensor. All three wires tested good.

Could it be the ECU? My ECU also had a failure of the voltage regulator. I wired in an external regulator until I could get the ECU repaired. I also have a P0443 code for EVAp System Purge valve, but I don't think it would contribute to this.

 

[macleanflood]

Try this?

Thread 'How to clean your IAC (Idle Air Controller) valve'

Jan 2, 2016

If you're experiencing idle issues on your Jeep Wrangler TJ the most likely culprit (and the first thing you should check) is your IAC (Idle Air Controller). Often times the IAC gets very gunked up causing the Jeep to idle improperly. A simple cleaning is usually all it takes to get it running as good as new.

If you end up needing to replace your IAC valve (they do fail on occasion), you can find the part numbers (and the links to purchase them on Amazon) below:

2005-2006 IAC Valve (Part # 4861552AC)
1997-2004 IAC Valve (Part # 4874373AB)

There is no need at all...

• Chris
• iac idle idle air controller idle valve
• Replies: 189
• Forum: TJ How-to Guides

• 

-Mac

 

[cpainter56]

What became of this? I’m dealing with the same issues

 

[CharlesHS]

For years I had the occasional random misfire for which I tried the usual things to resolve the problem.
While the things I tried (spark plugs, injectors, coil rail, CMPS, CPS combustion chamber cleaner, clean the IAC) decreased the random misfires; nothing resolved the problem.
When I had the clutch serviced by Happy Trails 4x4 they replaced the flywheel and noticed that there was a rust buildup on the CPS trigger blocks on the OEM flywheel along with a dusting of rust on the CPS surface.
Since then the random misfires have gone away.
I suspect the rust buildup on the trigger blocks and the debris on the CPS were the primary problems causing the random misfires.

 

[cpainter56]

I went back over mine yesterday, discovered the crank sensor had the wrong bolts, and the crank position sensor was 180 degrees out of synchronization. Fixed both issues and it’s running much better. I have a genuine mopar crank position sensor on the way to hopefully clear up what little bit of misfire remains. Cleared my codes and haven’t gotten another one.