Blown turbo or dead cylinder?
 

Hello all, first post here although I've been lurking a few months.

Should note that for the most part I know my way around cars, I drag race a Firebird on the weekends, and do all the work to it. I've had my 2010 SS/TC for a little over a year now, don't know exactly what the PO had done to it other than a charge pipe, down pipe, intercooler, and "custom" tune.

While driving earlier tonight, was going through the gears hard(ish), not redlining or anything, but making full boost (25lbs) nonetheless. 2 small pops that sounded like a backfire in 4th gear. Stopped at my desination, and smelled of burnt oil. Let it sit for a few hours, start it back up to head home, no oil leaks, no oil smell, runs seemingly normal. Stop at a red light, more burnt oil smell. Get it home (20 min drive) and in the garage, thick clouds coming out of the exhaust. Looked white, but definitely smelled of oil. The car seemed to drive fine the whole way home, but I didn't put any boost to it to risk hurting it worse.

Any ideas? Going to compression test tomorrow as a starting point.

https://i.imgur.com/AebLf2j.jpg

compression test would be a good place to start, take the intake off and check the compressor wheel for any oil/ endplay

Compression test turned out ok, cylinders 1, 3, and 4 at 150, cylinder 2 at 120. Going to dig in more and check the turbo.

From air filter to turbo inlet, a puddle of oil.

https://i.imgur.com/ER90hYo.jpg

2 is a touch low, its most likely the turbo is shot or there is some chance that you are getting lots of blowby from cylinder 2 and its pressurizing the crank/valve cover and blowing oil into your intake

cylinder 2 is a worry. that's kinda low compared to the rest

As much smoke it was making, and the puddle of oil at the turbo inlet, I'd guess the turbo is the bigger issue. That part is from the air filter to the inlet, so I can't imagine how so much oil would end up there if it wasn't the turbo.

Anything else I should look for as I unbolt the turbo?

it could come from the pcv line that vents from the valve cover to intake. check for any endplay on the turbo. if the turbo checks out fine i would try doing another compression test on all cylinders. if cylinder 2 is still down compared to the rest you can put a tablespoon of oil down the spark plug hole, if your compression bumps back up then you are looking at a ring/ringland issue

Just out of curiosity, where would you send in your turbo for a rebuild?

Is there any realistic way to check endplay with the turbo still bolted up? I can barely reach it.

I'm not sure, I have a buddy that races a turbo v6, he said he can help me rebuild it, but I don't know where I'd go to have it balanced.

yes, you can take your intake off and reach your arm back there, grab the compressor wheel nut and feel for any slop, just remember it is a journal bearing turbo so it will have a tiny amount

Can't say I felt any movement at all to be honest. The only thing that seemed out of ordinary is a slight metallic grinding noise when I put pressure up or down and spun the compressor.

the oil puddle in the inlet is definately from the PCV. All the turbo cobalts have it.

Has anyone rebuilt their turbo? Looking around for kits, and I've seen 2 that look like they could be for our turbos, but they don't specifically match up. Nothing really shows up when I put in the specific Borg Warner turbo part number. Even if the turbo isn't the issue, it has 90k miles on it, so a rebuild certainly wouldn't hurt. Not looking to upgrade my turbo right now, pretty happy with its power for being a daily driver.

Side note, I can't believe how tight some of these bolts are for being a 5 year old car...snapped 1 bolt off on the turbo brace, and started to round off 1 of the downpipe bolts before I stopped and let everything soak with wd40.

Update: rebuilt turbo, got everything bolted back up, still having the same problem. Idle is low and inconsistent.

I guess do another compression test and start heading in the direction of rings/ringland/valve seals. Ugh.

Ya like I said before, that one cylinder that's 120 is bad. If u have 3 at 150 and one at 120, there is ur problem. Rings are going out on the one, that or ur valve is sticking due to valve gunk, check ur valves for carbon buildup before u do rings

Another update:

Did another compression test, this time with oil in the low cylinder as suggested. Cylinder 2 (previously 120) shot up to 180 with a bit of oil.

Can't believe rings are shot after 90,000 miles, but whatever, the top end is already off in preparation for pulling the motor. Any tips on not screwing up timing/direct injection?

look up lsj build book it has lots of info on taking the engines apart. by top end you mean you already have the cylinder head off?

Head and cams are still on, haven't messed with timing chain. Valve cover, intake, exhaust manifold, and turbo are all off. Wiring harness is disconnected from almost all of the engine components.

injectors are simple, just 4 bolts and undo the fuel line. be carefull not to damage them when puling it out. there are timing marks and coloured links on these engine. you are going to need a fair amount of tools like E-torx bits ,1" wrench(s) 1 1/4" socket, impact wrench ect...

My car had 55k miles when i had the same problem

What's the process on this? Am I pulling the chain and gears off the cams? I'd prefer to pull the head without messing with the rockers, springs, or keepers.

valve springs and cams can stay in. basically at the very least to take the head off in the car you need to remove: turbo,intake manifold,exhaust manifold,valvecover, timing chain, injectors,coolant lines. there is a detorque spec aswell when removing the head studs

Motor is out and torn down. The issue was a cracked ringland on cylinder #2. Cylinder looks okay, valves and combustion chamber look okay aside from being dirty. It's actually lucky that this ringland broke, because #4 rod bearing was coming apart, but the ringland issue appeared before the rod bearing did any damage to the crank.

Ringland:
http://imgur.com/mz0Mtdb

Rod bearing:
http://imgur.com/8TJPoj8

Going to put a set of pistons in, bearings, timing set, gaskets, bolts, and a throwout bearing for the clutch. I'm assuming that main bolts are torque to yield, anyone know of a source for them? Going through ZZP for most everything else, although their timing kits are out of stock.

Not many people spin rod bearings, go long intervals without changing oil? Lots of rpm?