I did both just after getting the truck. No debris in the filter, nothing came out of the pan when drained. Knock continues with RPM, does not leave, truck runs and drives down the road fine at 75, just knocks like it wants to come apart LOL

 

Just to throw this out there to keep in mind, a fuel injector starving for fuel will sound like a hammer banging on the block and the internals are about to come apart.

That doesn't fit any of the rest of your symptoms, and cruising down the freeway at 75 with no issues isn't an overall fuel restriction, but just in case you've got an injector acting crazy or something.

I'd pressurize the coolant next. Leave the oil fill cap off so you can listen there for any sounds. I'm wondering if you've got a hole or crack in your front cover.

 

I've swapped injectors, with 2 known good sets (both another set of ABs, and a set of AD), no change. I swapped UVCH, rockers, and push rods, no change either. The only thing I didn't change is the IDM, which I guess could cause the issue, but I'm not sure if an IDM off a 2002 will work in an e99. The sound is always from injectors 1/3, I can hear it loudest at the exhaust manifold, its not coming from the pan, and it's not coming from the valvetrain, as it's mostly quiet when listening from the top. I imagine it's something in the cylinder itself, but I figure if I'm pulling the heads off to find out, I may aswell pull the engine out and swap the other one in, as they're probably about the same amount of effort

 

What if the PO filled the fuel tank with gasoline? Or the tank is full of water? Have you checked fuel filter condition? Smell?

 

When I got it, it had 1/8 of a tank, I filled it up and added stanadyne, I changed the fuel filter and it looked and smelled normal, no discoloration, nothing abnormal.

 

What CPS do you have? Some have been known to cause 3 and 8 to be louder. It's a cheap thing to test. If you've got spare injectors, I'm guessing finding a spare CPS won't be too hard.

I'd pressurize the coolant reservoir before I pulled the heads. Maybe you've got a hole in the front cover that's giving you the chocolate pudding. If so, you should easily hear air from the oil fill cap I would think.

 

I haven't actually checked the CPS, I've never heard of one causing this sort of issue, but I'll see which it has and swap them around, I'm sure I have 3-4 of them sitting around somewhere.

I probably won't pull the heads, if I'm pulling the heads, I'll just pull the engine and put the other in, path of least resistance. I'm going to pressurize the coolant system once I get back from my trip this weekend and see what things look like.

 

I figured I'd post an update, ended up just yanking the engine and swapping it on a gut feeling. Truck is up and running again, but I finally tore the cylinder heads off the old engine today. Head gasket blew on cylinder 1, piston has wear in the corner as well, haven't gotten to look at the bottom end yet, curious to see how the cylinder bore will look etc.

Truck was stock with a ts6 chip, all other 7 pistons look absolutely spotless, and from what I can see the cross hatching looks perfect too.

I'll be curious to see if there's any other damage down farther, or if this was the entire root of my problem.

 

Ugh, but thanks for the update.

 

I would say that was your problem. Wonder if a ring broke, or it just got hot. Heck if it isn't to bad, you could pull the piston, hone new rings and piston and have a spare engine. Well I'd check the head surface as well. Some would do this, me I'd rebuild.

 

I tore the pan off today, and it did infact blew apart the piston skirt, the cylinder doesn't look awful, but there is some minor scoring and would probably need sleeved. Rod looks fine, thankfully it was a forged rod truck, the PMR might have broken in a similar circumstance.

 

Don't know what a sleeve would cost, but one sleeve is no big deal. I believe the new pistons have a heavier piston to stop this. Redesigned anyway. Where are you at? Guys look for these motors to rebuild all the time if you don't want to keep it.