Car: A6 C7 (2014) 2.0 TDI 190HP S-tronic (Currently 211,000 km on the odometer)
Issue and symptoms: P0016 error code (camshaft / crankshaft incorrect correlation) ; MIL ON with glow plug light flashing ; rough engine at higher RPMs ; lower top speed and slower acceleration ; occasionally hesitating to turn on the engine (engine is cranking but takes up to 10 sec to turn on) ; driving uphill with cruise control drops speed for approx. 5 kmh (let's say from 80kmh to 75 kmh) and only after that the car drops in lower gear and speeds up to 80 kmh again.
How it all started: I have changed the timing belt at around 209,000 km. Because that was my first time to change the belt, I was following steps written on ElsaWin. It was written that after putting the new belt and tightening the tensioner, the next step was tightening the camshaft and HPFP sprocket to 20Nm, and to turn the crankshaft by hand to check the timing (I'm writing this because it seems that I haven't tightend the nuts to 20 Nm but less...).
As soon as I turned the crankshaft by hand, it seemed like camshaft sprocket slipped or something. I heard a quite loud hitting noise and saw the small locking bolt move to it's most far position (it was in the middle). However, I continued turning the crankshaft for two rotations, and when it returned to TDC the timing was spot on. Crankshaft pin, camshaft pin and HPFP pin were just on the right place. Even the small locking bolt on camshaft sprocket was back in place, in the middle where it was originally. After that I have tightned everything to it's final torque and put everything back, turned on the engine and made a test drive. Everything was working perfectly. I drove it few weeks without any issues. BUT, one day I was driving a bit aggressively, uphill at around 4,500 RPM for a bit, and when I came to a stop, I heard the engine noise was a bit rough, and it wasn't accelerating as fast as it should, just a bit slower. No MIL so far. The next day when I turned the car on, the MIL was on and the same rough sound and slower acceleration. The day after my wife drove the car, and she experienced something much worse. She reported that the car wouldn't want to move, only when she hit the accelerator to the floor, the engine was "suffering" but was able to drive back home (it was close, about 500 meters). She smelled something burnt... Later, I opened the belt cover and I saw the belt slipped a few teeth, and the belt was damaged on few places. Moreover, I have found a broken piece of camshaft sprocket (circled in the picture). Long story short - the car was later towed to a mechanic.
Things that my mechanic checked and replaced: After that unhappy event, the car was towed to a mechanic. He changed the broken camshaft sprocket, put a new toothed belt, and adjusted timing of the engine. He says the timing is now correct regarding the belt, but he can't get rid of the P0016 code. He suspected the VVT solenoid could be faulty, so he replaced the solenoid also. However, P0016 is still active. He now suspects that the whole VVT system is faulty, or that the camshaft is damaged.
My questions are is there any chance that the problem is something silly like a sensor, faulty belt tensioner, damaged crankshaft sprocket, or contaminated oil? What is the best way to start investing? As the mechanic is not 100 % sure, I don't want to start changing parts that are actually working correctly... Like the VVT operating valve, to me it seems that the old one was working the same as the new one...
I have genuine VCDS so please advise me is there anything I can check using diag.
Service history of the car: All maintenance was done in dealership prior to the timing belt change. The engine oil was changed at the same time as the timing belt (2,000 km ago). The only service proof I can't find is for the fuel filter. It seems that the fuel filter was not changed since 125.000 km, but it should be changed every 60.000 km.
P.S. Please don't criticize me, I'm aware that I have messed up, and that the problem could have been avoided. But I'm a car lover and I love to maintain my own cars, it's my hobby... So I'm here to get your help, not to listen how I screwed up... thank you!
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