Vehicle is a 2012 W166 with M276.9. with 93K miles. Dove in to address startup rattle and a stored P01177 DTC. No check engine light. Job escalated from there.

Expected a bad secondary tensioner (since the engine has the early tensioners with no check valves). Also, the intake manifold was full of oil, dripping from the ports when removed. Also found that the Bank 1 intake cam adjuster was toast - likely the cause of the startup rattle.

So I got some GB and cleaned the backs of the intake valves and cleaned the intake as best I could and installed:

New Bank 1 cam adjuster
New Check valves and both updated secondary tensioners.
New intake gaskets- upper and lower
New oil drip pan

And while I was in there..

New cam position sensors
New cam solenoids and pigtails

I timed the Bank 1 cams by sighting the reluctor wheels through the CPS magnet holes and they lined up as they should. Also noted that my cams do not have any laser marks to check for tone wheel slippage.

Got everything back together and it runs awful. Check engine light and multiple codes for misfires and a bad gallop when spinning on the starter. Clearly, it has low compression on a couple of cylinders. I'm 100% sure no valves got kissed by pistons.
Thought maybe the Bank 1 intake cam reluctor wheel might have slipped so ordered a new cam but the reluctor wheel is in the same position on both cams. And the new cam (Genuine BMW from FCP) does not have laser alignment marks for the reluctor wheel either.
That leaves the exhaust cam reluctor wheel, but no codes were thrown for that cam before the tear down.

So, here are the questions:

- Is there any way to check if the reluctor wheel is in the correct position on the exhaust cam if there are no laser marks?
- Is there any way to time the cam by cam adjuster position or lobe lift to see if the reluctor wheel slipped?
NOTE - I've looked at the WIS info on aligning the two Bank 1 cam adjusters by how they point at the tensioner and the picture seems vague. I've yet to find a head on picture of the Bank 1 cam adjusters in place to accurately check the alignment of the cam adjusters themselves.
- Is there anything else I could be missing?

Advice appreciated

Mariner1

 

Congrats on doing everything really well... now you just need to finish the last few steps.


From your description I understand your Bk1 timing is likely off and Bk2 having no issue, correct?


The target positioning is not only Bk1 but everything timed all at once:

• crankshaft balancer pulley marks
• Bk1 : Intake + Exhaust VVT (Reluctors slots)
• Bk2 : Intake + Exhaust VVT (Reluctors slots)

The camshaft reluctors slots being on time or not will trigger a fault from CPS signals being incorrect.

The most important being the valves not kissing pistons.
Manual rotation check before cranking.
All 4x VVT marks alignment with crank. When engine is on-time reluctors will show correctly.

Its all very trivial but details are not simple. Take your time checking where exactly is your issue... hopefully 1-tooth off not one full turn.

Lastly for pigtails... the leakers are CPS more so than VVT solenoids. Extreme HEAT burns off the plastics...
New CPS + 3-Wires "pigtails".
🤞