1999 jeep xj runs like crap. p1391

meatheadwes

meatheadwes

Well-Known Member
Joined
Nov 8, 2009
Location
kings mountain
99 jeep xj 4.0l 25k on a rebuilt engine. was throwing codes for a crank sensor this past september. it finally died on the way to put deer corn out. drug it home and replaced the crank sensor after letting it sit for a couple months. cranked it up and it ran great. drove it to the car wash a couple miles away to wash all of the trash off. went to crank it back up and its popping through the intake and back firing. throwing a p1391 code for intermittent loss of cam or crank position sensors. have since replaced both crank and cam sensors twice. cap, rotor, and coil pack also have been changed along with pcm. and looked at the wiring. still runs the same no power just popping and back firing. dos anybody in here have any idea on what the hell is going on with this thing. fixing to part this shitter out.
 
NickMaul said:
Follow the CPS wiring into a larger bundle. Make sure it isn't rubbing agains the intake by zip tying it to the rail or something secure. I had that issue once before.
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gonna check again tomorrow but i cant find anything
 
A stretched timing chain will cause this.
 
Maybe @Jody Treadway can chime in but wasn’t there a stretch where distributor gears had issues on the 4.0? Maybe what’s causing the timing issue assuming everything else with the rebuild was good to go.
 
Has it ever ran well with the rebuilt engine? Any chance the dizzy isn't synced correctly?
If it's an electrical issue, inspect the engine wiring harness where it wraps around the back of the head at the rear driver stud. They chaffe there
 
If you’re throwing the parts cannon at it, try the fuel pressure regulator, idle air control valve, and double check the screen on the fuel filter.
 
Jody Treadway said:
Has it ever ran well with the rebuilt engine? Any chance the dizzy isn't synced correctly?
If it's an electrical issue, inspect the engine wiring harness where it wraps around the back of the head at the rear driver stud. They chaffe there
Click to expand...
Ram great for the last 3 yrs then all of a sudden it quit. Wasn’t showing rpm signal on my scan tool changed out the crank sensor it started and ran fine. Drove it a few miles then it started what it’s doing now. Change the crank sensor again still runs the same. But it’s throwing cam and crank sensor codes for Intermittent loss of signal
 
wiggle the connector for the crank sensor
 
Send me your email and I'll send you the service manual for a 99. Will have the pin out for your harness and connectors. You can ohm it out or hack probe for 5v reference.

I still say timing chain
 
Mine was way off of cyl.1 on the dizzy when at top dead center and zero on the timecover.
 
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