Long story short, Cylinder 4 started constant misfiring, towed the car, assumed valve seat fouling, rebuilt entire engine. First starts after rebuild, cylinder 4 is still constantly misfiring. I believe cylinder 4 to be the closest to the timing chain, opposed to cylinder 1 being closes to transmission.

The next thing I can think to do is pull the ECU and CAS and find somewhere to send them for testing, and I'm grasping at straws with that. Maybe someone has further diagnostics I'm not considering, or how to test DME/ECU, or knows where to send them.

Longer Story,
Did the obvious tests again, swap spark plugs, swap ignition coils, check compression. Everything is fine, but cylinder 4 is still misfiring. Thought about "resetting adaptations" with the scan tool, but that doesn't immediately make sense to me because the other 3 cylinders are running fine. Did I do the timing chain wrong, well, the other 3 cylinders are running fine and the compression is good, so it can't be that far off if at all.

I'm desperate. I've taken up my neighbor's barn for months with this rebuild and have nothing to show for it. Any/all advice would sincerely be appreciated.

Even longer story,
Normal day, car running fine, accelerated down a highway on ramp and during acceleration the misfire began just like a light switch. Swap plugs and coils, check compression, all ok 160+ psi (spec low limit is 8bar/117psi). Borescope in cylinder 4 showed dry flakes of carbon in the combustion chamber, which led me to assume valves not seating correctly due to obstruction causing misfire. After removing the cylinder head, and seeing the valves were closed fine, I pulled the pistons. Everything fine there also. Honed cylinders, replaced piston rings, replaced cylinder 4 fuel injector, cleaned and lapped valves. Used torque specs for just about everything during reassembly.

Thanks

 

It was an intermittently failing ignition coil. Never had one be intermittent before.

 

That was the root cause to all the work you had to do?

 

FYI, cylinder 1 is timing chain end, and cylinder 4 is transmission end. For a mis-fire, I would always start with replacing plugs and coils. Last resort should be engine rebuild. You should be good for a while now, I hope!

 

I replaced all my coils with the plugs a while back just as a maintenance item due to all the various posts about intermittent coil problems after I got a misfire warning. The typical swapping of coils to troubleshoot don't work with that intermittent scenario...

 

2014MC:
I certainly hope not, but it's not impossible. I believe the original issue was carbon fouling on the intake valves of that cylinder. Before the rebuild, it was always cylinder 4 misfiring, regardless of mixing and matching ignition coils, and mixing and matching spark plugs. Note I had admitted to believing cylinder 1 was cylinder 4 initially, but I did mix all the coils. Is it possible the car was lying to me about it always being cylinder 4? I suppose that is possible. And I suppose there is a 1 in 8 chance when I got the engine back together, I put the same coil back into cylinder 4 (though this shouldn't matter, because I mixed up the coils before disassembly and still had a problem on #4). After the rebuild, the misfire detection counter followed the bad ignition coil. I kind of panicked when I made this thread, I should've done more work before positing it, and for that I apologize.

If I'm wrong, and I did rebuild the engine over a bd ignition coil, it's not all bad. The intake valves were absolutely NASTY, and did take a fair bit of lapping. With a borescope, there were visible chunks of carbon in a couple of the combustion chambers during original misfiring. The turbo was shot, the wastegate actuator wouldn't pull the gate closed all the way. The oil control rings on the pistons looked absolute trash, lots of carbon build up around the 2 compression rings. I had an intermittent front crank seal leak, in this process I replaced the crank hub that runs against that seal. Other bits got replaced along the way.

She runs way better now than before the misfire started. Except, with a long slow uphill, it kind of chugs. It's like the jmtc JM40 turbo is giving the motor more power than the motor called for, and the motor is in a loop of asking for more boost, saying it's too much boost, asking for more boost. I assume if I took it for a tune this would go away.

njaremka:
Yeah... if I was a complete idiot, it's not all for nothing.

My apologies for the long answer, I figure more info is helpful for someone who finds the thread.

 

Yeah it makes sense if swapping coils around and the misfire remains at the same location that the coils are not the root cause. Hope you are able to figure out the chugging issues, assume you're not getting any codes or feedback from the computer (yet) on that one.

 

I appreciate your responses friends.
Early on post-rebuild I did get 2C90, "Diverter valve jammed closed" or very similar verbiage. Didn't tun on engine light, just noticed it in the code reader as "not present" but in the memory. Posts I found while looking into that have said "it's just a tuner code" and so I took it as unimportant. On the highway home at 70mph, there's one long hill is where it chugs. I shouldn't say chugs like it is underpowered, it feels like it starts making too much power such that the ECU determines it will end up faster than cruise control is set to, backs off the boost prematurely, and it happens a few times up that hill. The turbo is certainly, at least, making boost, as it pulls strong through 2nd gear. Well, as much as an almost stock R60 can "pull." It's a fun car to drive again, I can at least say that.

 

Sounds like the drivability issue and that history code may be interrelated then. Not there all the time. The car sees it at some point and you sense it as well driving. I certainly enjoy learning from your learning and you have a good head on your shoulders.

 

You're probably right. I don't think I'll get an answer to that one unless I take it to someone with a dyno.

Thank you, that's very kind of you.