• NAXJA is having its 18th annual March Membership Drive!!!
    Everyone who joins or renews during March will be entered into a drawing!
    More Information - Join/Renew
  • Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

2000 140k - p303 code when above 3k rpm - NOT heat soak

jhamilton

NAXJA Forum User
Location
NJ
Cold or hot start up no issue: Consistent above 3000rpm misfire throw p303, every time all the time. Can drive up 3000 rpm without any issues, but once past... it throws code p303 and the misfire is felt.

Replaced ecu (other issues), cps, coil rail and plugs. I also replaced the o-rings on injectors 3 and 4 as well swapped them. When I replaced the leaky valve cover gasket. I saw no coolant on the top of the head by cylinder 3 ( of course could be crack still).

History: XJ's PCM was damaged due to reversed polarity jump start. Bought one online...

-Is there a chance the PCM used could be bad and cause this?

-What's next on the list to check?
-331head?
-compression?
-injector wiring?


Thank you all.
 
Cold or hot start up no issue: Consistent above 3000rpm misfire throw p303, every time all the time. Can drive up 3000 rpm without any issues, but once past... it throws code p303 and the misfire is felt.

Replaced ecu (other issues), cps, coil rail and plugs. I also replaced the o-rings on injectors 3 and 4 as well swapped them. When I replaced the leaky valve cover gasket. I saw no coolant on the top of the head by cylinder 3 ( of course could be crack still).

History: XJ's PCM was damaged due to reversed polarity jump start. Bought one online...

-Is there a chance the PCM used could be bad and cause this?

-What's next on the list to check?
-331head?
-compression?
-injector wiring?


Thank you all.

When you had the valve cover off did you closely examine the #3 valve springs?
 
-What's next on the list to check?
-331head?
-compression?
-injector wiring?

Had the same problem with a 2000 XJ, anything over 2500-RPMs would set a flashing CEL (P0300, P0303 and P0304).
Turned out the cam synchronizer's clamp wasn't tight enough and it had moved about 20 degrees from where it should have been. Reset the synchronizer back to Factory specs and the codes went away, no matter how high the revs.
Checking it doesn't cost a thing except for your 1/2 hour of your time.
 
Had the same problem with a 2000 XJ, anything over 2500-RPMs would set a flashing CEL (P0300, P0303 and P0304).
Turned out the cam synchronizer's clamp wasn't tight enough and it had moved about 20 degrees from where it should have been. Reset the synchronizer back to Factory specs and the codes went away, no matter how high the revs.
Checking it doesn't cost a thing except for your 1/2 hour of your time.

As it turned out the camshaft sensor needed to be reindexed. Thanks guys.

http://www.jeepforum.com/forum/f11/how-reindex-camshaft-position-sensor-1145301/
 
Back
Top