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low compression on bank 1 120-bank 2 180,timing chain?

Possible. Ya could confirm by setting cyl 1 to tdc and pulling valve cover to check mechanical valve timing.

that was my next step,but if it is off which chain,this motor has 3 chains,left head,right head & crank

You need a special tool and have to have it. do all chains, cassetes etc. its gotta be the chain in this case unless a gear broke which is highly unlikely

let's not get away from ourselves here. there are a few other issues here to consider. lets do a cylinder leak down test here. i work on a bunch of these bombs and i gotta say i've replaced chains by the bucket full usually because they were driven for a period of time with broken guides or the infamous lower tensioner. i've never seen a chain cause a compression issue on one of these. i've seen loose enough where you can't see why it didn't but never have. however i have run into issues because of the runners in intake manifold. i think the updated intake covers this year as well. a flat no power issue with the readings you gave really doesn't add up. you may have an unbalanced idle but lack of power i don't think would fit into a mechanical issue here. mass air flow sensors will still (i don't know why) show good with a scanner and cause issues like this. i've seen fuel issues cause this. check volume as well as pressure. was there an issue with stuck regulators? mmmmmmm, i'm still thinking here and can't scan the bulletins but the intake issue is still whirling around the room but that has always (in my experiences) thrown a code. a quickie here, if you do ever replace the intake with the update i suggest using the old bolts not the supplies ones. they have to be cut down to fit. make them about 1/4" longer. i had a few that stripped on the third run on the tightening. back to point here. i'd be inclined to look at the maf. if the engine doesn't sound like a cement mixer full of marbles the chain is probably ok. if you do decide to change the chain yank the mill, check to see if this is part of the intake update, look for coolant dye stains on the block and if there are dye clusters you may want to replace the gaskets. speaking from experience it will probably start leaking soon after you return the vehicle.

I did r&r the intake & checked for leaking injectors. Injector reading at #1 bank 2.3, #2 = 4.9 on the scanner.

I think one of chains is out, but has anyone seen chains go out at 65,000 miles on this motor?

for a chain to be out enough to cause this it would sound like a cement mixer. has this ever overheated? i know that i have all the little toys of the industry and readily admit i'm a tool geek but if i had my way i'de be inclined to take my snappy camera probe and take a look at the cylinders and compare banks. i have experienced issues similar to this from overheating issues.

I'd be inclined to lean in the timing chain direction. However to assume that the chain has jumped is somewhat presumptous because I have seen those sprockets shift on the camshaft. Assuming all else is ok, I'd be getting customer permission for exploratory surgery on this one and remove the front cover (and all that entails) and simply be checking the chain timing. And, yes, it does take an assortment of specialty tools for this one. I have them and use them. Nice dollars for the stuff but so far as I know is the only way to align the several chains on this animal. Am I right that bank 1 is the right bank? If so, there is a chain to the rear of the cylinder head. And if my memory serves me right, the only way to check that chain is engine r&r. Yes, this 4.0L is a strange one.

for compression to be that different from one bank to the next it has to be a t chain. Power can be caused by other things but and even compression loss from bank to bank?

We removed the engine to check the chains, the timing chain on the right side was off due to a bad chain guide

tony1981 wrote:We removed the engine to check the chains, the timing chain on the right side was off due to a bad chain guide

Like broken - missing? I am curious because I will add it to my collection of possibilities on these engines.

Thanks for the update. I do appreciate it.

there is a load tensioner near the bottom of the chain that breaks and the chain slap will tear a guide all to heck. personally i've never seen a chain jump, see a lot loose though...........there must be a good amount of debris in the pan.

the engine had a lot of debris in it, when the guide broke it ate in to the cylinder head.

By the way we are installing a rebuild engine,thanks Tony

hope it's a jasper. best reman parts i've ever used with the best warranty........a bit more expensive but well wort it. call martha at x2935. don't tell her i said to call...........