4.0 timing chain question

[Joscibo]

I bought an 04 yesterday which I am guessing has a bad engine due to timing chain issue. It has a hole in the back passenger side valve cover but it still runs. The previous owner drove it home 5-10 miles after it happened. I bought the truck for parts for $700 and hauled it home to part it out. I need a bunch of parts for mine and can sell other stuff to pay for the ones I take. Is it possible to fix this 4.0 if indeed the problem isn't fatal yet?

 

[03explorereb]

there's always hope. the fact that it runs at all means it is possible to resurrect the engine. but not without a lot of dismantling to clean the inside. there are small pieces of chain guide that are already sucked up into the oil sump, not to mention various other pieces of debris scattered throughout. a lot of work and a lot of time must be dedicated.

 

[03explorereb]

...that is, assuming the problem deals with a bad chain or tensioner. if it skipped time, which happens due to the fact the these engines have cams with no keyways for the timing gear, then it's very possible that it might have bounced a valve or two off of the pistons. a compression check while it is still together might tell you a lot.

 

[Joscibo]

...that is, assuming the problem deals with a bad chain or tensioner. if it skipped time, which happens due to the fact the these engines have cams with no keyways for the timing gear, then it's very possible that it might have bounced a valve or two off of the pistons. a compression check while it is still together might tell you a lot.

It has several engine codes for cylinder 1,2,3 misfire and several misfires detected. It also has system lean bank 1 and bank 2 and misfire detected at startup first 1000 revolutions. I'm not sure if this helps distinguish if its junk or if it can be fixed?

 

[03explorereb]

the engine has jumped time on passenger side cylinder bank, due to what i would assume is a faulty chain guide or a bad backfire which might have loosened the cam sprocket to the cam causing the issue. it's very likely that this engine is done. a compression check would need to be done to determine whether or not a valve has been bent. lot of work but it can be done. more than likely this engine is damaged requiring a little more than a minor repair to the chain guides. just my opinion.

 

[2000StreetRod]

check the compression

. . . a compression check would need to be done to determine whether or not a valve has been bent. . .

I agree. Check the compression before parting out the vehicle. No compression on the right bank probably means valve damage and not worth rebuilding. Low compression (50 psi or greater) probably means slipped chain but no valve damage. Misfire codes are due to low compression. The engine has been running with a broken rear cassette guide long enough to allow chain slap to eat thru the valve cover. Lean codes may be due to unmetered air entering the crankcase thru the valve cover hole. The 2004 has the improved timing chain components but the traction side of the right cassette guide assembly is not reinforced with metal and still breaks with age.

 

[03explorereb]

I agree. Check the compression before parting out the vehicle. No compression on the right bank probably means valve damage and not worth rebuilding. Low compression (50 psi or greater) probably means slipped chain but no valve damage. Misfire codes are due to low compression. The engine has been running with a broken rear cassette guide long enough to allow chain slap to eat thru the valve cover. Lean codes may be due to unmetered air entering the crankcase thru the valve cover hole. The 2004 has the improved timing chain components but the traction side of the right cassette guide assembly is not reinforced with metal and still breaks with age.

ditto.
the engine will have to be removed because the rear chain and guides cannot be serviced without it. a compression check will be much easier to do with the engine out. once out, i am sure you will get a much clearer picture of what damage has been done. one simple check that can be done while the engine is still in the engine bay is to check the relation of the camshafts to each other with piston at tdc in the #1 firing position. note the slots on each camshaft and their relation to each other. review 2000streetrod's thread on timing the 4.0 sohc to get a better idea. one note of caution: turn the motor over by hand, so no further damage ensues.

 

[Joscibo]

We will check that out. Thanks guys. I have figured that there is a good chance it's hatched but thought I should ask here to see what to check out. If the engine is somewhat salvageable to find out now before we start tearing into it. Thanks.