04 Mounty Jumped time bank 123

[seaquell]

Hi has anyone ever had a timing chain jump or slip.
A guy replaced all the tensioners and guides a year ago on my 4.0 SOHC
when towing hard ,the other day it started missing and blinking the check engine light.
I looked all over for vacuum leaks and wires but bank 123 is at 120 PSI and bank 456 is at 150 PSI,
maybe the guy didn't tighten the cam bolt enough on the 123 cam?

Can I take off the valve cover and re time the 123 bank cam sprocket?

 

[seaquell]

fixed it

I took off the valve cover and put 2 pin punch timing marks one on cam-- one on the sprocket--.
loosen the cam sprocket "left hand thread" then index back about 1 tooth or 1 centimeter on cam. compression went from 120 to 80 psi oops WRONG WAY!
Moved it 1CM forward and ITS AT 210 PSI like the other cyl. bank.
Put it back together and its GOOD. no codes no rough idle and missing.
I solved it myself but maybe it will help someone else.
Also I used 2 pair of locking pliers to hold and move the cam kind of walk it little at a time.
Best Wishes

 

[2000StreetRod]

Accurate timing

I took off the valve cover and put 2 pin punch timing marks one on cam-- one on the sprocket--.
loosen the cam sprocket "left hand thread" then index back about 1 tooth or 1 centimeter on cam. compression went from 120 to 80 psi oops WRONG WAY!
Moved it 1CM forward and ITS AT 210 PSI like the other cyl. bank. . .

The accurate way to time the camshaft is to tighten the camshaft sprocket retaining bolt when the timing slot is below the axis of the camshaft and parallel to the head surface that mates with the valve cover.

Your first post stated the bank 2 compression was 150 psi. Your second post stated the bank 1 compression increased to 210 psi like the other bank (150?). The typical compression for a correctly timed camshaft is about 180 psi for a warm engine at WOT.

 

[seaquell]

Thanks 4 info

Hi
thanks for the pic, I can tell it jumped a tooth because it had scuff marks on the valve cover from the chain rising over the teeth, I am glad you posted the pic for me I thought the slot was on the back of the cam gear now I see its on the front of the cam shaft. I wish i seen that before i put it back together!
Anyway ,I had 180 psi when cranking 2 or 3 revs, but i found after cranking 5 or 6 revs it would top out at 210psi on my tester.
It runs fine now and I am replacing my tensioner also to help prevent this from ever happening again!