Hi Everyone,

First time posting, please let me know if I posted incorrectly or in the wrong place. Thanks in advance for any help you can offer for this situation that has me stumped.
I'll try to keep this short because the story really is quite long. I own a R55 Clubman S 2008. It has ~130K miles on it. I've honestly never driven it because I was actually given it for free because the engine was failing.
It would idle rough, give out barely any power and would frequently shut off completely when coming to a stop. I'm not an expert mechanic, just a hobbyist, so I really wouldn't have taken on this project if the car hadn't been given to me for free. Other than the engine the car seemed in good shape, no dents or anything so I gave it a shot.

I first did a compression test and found 0 compression in cylinder 3. So i thought it was a bent or broken valve, which was alright, i was planning a long term project so let's get going.
Took me several months of weekends tearing the whole front apart and taking the head off but eventually it was done and i found a cracked valve on the exhaust, also incredible amounts of carbon buildup everywhere. Pretty sure the carbon is a common issue in this car.
Anyway, let's speed things up. I thought while I have this whole thing apart let's replace some of the common wear parts and anything else that may be a problem. So to spare you the long story here's a list of things i did and parts i replaced:

1. Total head rebuild. Completely cleaned and resurfaced at a professional shop, looking brand new.
2. Brand new Valves, all 16 of them and Valve stem seals (checked compression after rebuild, a bit of variance but all cylinders are between 150-170
3. Brand new timing assembly, chain, sprocket, guides, bolts, Vanos sprocket. The only part of the head I didn't replace were the camshafts themselves.
4. Brand new head gasket, obviously
5. New Crankshaft seal and Crank Bolt
6. New water pipe behind the engine block since i know those fail.
7. New Thermostat and some new tubing that had worn out.
8. New serpentine belt
9. New Belt tensioner
10. New Water pump wheel
11. new triangular turbo gasket seal.
12. new exhaust manifold metal gasket
13. New Oil pan, oil filter, and synthetic oil.
14. Replacement aftermarket turbo oil line. (https://www.ecstuning.com/b-nm-engin...nm.498858~nme/)
15. New OEM Turbo Oil return line.
16. All new Turbo banjo bolts and seals
17. Brand new vacuum pump, because those tend to fail.
18. Brand new spark plugs, Bosch iridiums.
19. New low pressure fuel feed line, (broke the locking plastic on the old one while removing it)
Probably a half dozen other small seals and bolts I cant remember...

After putting her all back together I started it up. Ran great for about 2 minutes but started to put out some white smoke on the exhaust side and started shaking and misfiring.

I plugged in my OBD reader and got these codes:
P0300 Random/Multiple Misfires detected
P0301 Cylinder 1 misfire
P0303 Cylinder 3 misfire
P0304 Cylinder 4 misfire
P0327 Knock Sensor Circuit Low
P1497 (Which from googling looks like an throttle downstream air leak??)

After Triple checked the Timing (It is PERFECTLY in time. With the flywheel hole lined up on the bottom of the engine, the timing kit holders slide with no resistance onto my camshafts. not even 1 degree out of time.), a lot of googling and double checking all my connections I replaced these parts to try to fix this issue.

1. Fuel filter (which was yucky glad i changed it)
2. Valve Cover with the PVC with a brand new one.
3. Entire Intake manifold and Throttle assembly
4. Brand new Spark plugs AGAIN but this time with brand new coil packs.
5. Brand new fuel injectors with new seals.
6. New Knock sensor

At this point I'm at a complete loss. The only items related to combustion I HAVENT replace on the car is the High pressure fuel pump, which seems to be working because my fuel rail was pressurized when i went to replace my fuel injectors, and the pistons themselves!.
I honestly don't know what to do anymore. At this point I'm just going to start replacing sensors even though they haven't thrown error. New Camshaft position sensor, new Vanos solenoid sensor, new O2 sensors upper and lower, ETC.
At this point it just seems like it doesn't want to run no matter what. 50% of this engine is new parts and it's still misfiring and throwing the same error codes on every part replacement.

More info:
Like I said before compressions is good in all cylinders.
When removing ignition coils and spark plugs the plugs are blackened from misfiring but there is no oil or liquid seen on either component.
I don't get a misfire code for cylinder 2 which is interesting, only misfires on the other 3 cylinders.
I tried swapping around sparkplugs and ignition coils, Cylinder 2 remains the good one.
After every part swap i cleared codes and checked the OBD again and all codes remained identical.
The car wont run for more than 10 seconds unless you really give it on the gas and force it to keep running. If you just try to let it idle it'll die in seconds after starting.

Thanks again for any suggestions in advance!

 

In case anyone comes across this post in the future, I'm 99% sure i figured out the problem. It was a faulty VANOS solenoid. Not that it was dirty because i made sure to clean it when i rebuilt the head. But the solenoid itself seemed to have failed and was messing with my timing causing the engine to sputter and die. Replaced it with a brand new solenoid and she's running pretty stead now, a few more issues to iron out but no longer any RPM fluctuations or premature shutoff.

Special thanks to this dude and his channel. Apparently the Vanos solenoid can fail and throw no codes. He had a similar issue to mine so i thought i would try what he did.

 

Most of the time its the clogged vanos. I think the clogging makes them fail even after they are cleaned out, like it beats them up and they fail. The updated units also have the screen.

Glad you got it fixed.

https://www.northamericanmotoring.co...26-pcv-or.html

 

Hmm, I missed the thread and posted in the wrong one. Sorry