I rebuilt this engine completely over a year ago, 90% redone due to an overheat incident that pretty much cooked the synthetic oil to a crispy ball of black tar.
After putting it all back together I kept getting a code for the intake Vanos that I did not replace after rebuilding. The code was 2A7C. This happens at start up and it is a cold start code, but it triggers whether hot or cold, RPM jumps a little to 1200 and goes back down registering the code. The car has been driven with the code and it ran perfect. But now I have to smog the car and decided to dive into it.
What the issue is the Vanos gear cannot be retarded during the ISTA test from being at maximum advanced of 120 degrees and failing to come down when the test requests it.
After watching one YouTube video that mentioned the 2A7C code I decided to change the Vanos gear. I replaced the gear and put everything back. I turned it on it and right after starting it now registers OBDII code P052B(Cold Start 'A' Camshaft Position Timing Over-Retarded BANK 1) and the 2A7C is being shown under the different testing area for Vanos. The car runs perfect full power. I used both ISTA 4.32.15 and a bidirectional scanner Autel 708TS for testing. Before the gear was changed the fault code would also be triggered right after a rise in the RPM after which the car drove fine.
It seems the VVT system including solenoid, Activator, Vanos Gear timing and/or electrical connectors could be involved. When I replaced the original Vanos gear, I did redo the timing properly.
I did the relearn and adaptation also. Today I just checked the electric connectors to the 2 Vanos solenoid, with continuity to the DME short connector number 5 for intake and number 18 for exhaust and they are fine, I also get 4V on these lead DME wires. I get 12V at the second wire on both connectors. I also took out the Vanos solenoids and tested between prongs and get 11.3 ohms on both. Appling 12V also triggers both solenoids fine. One is original and the other off the market. I swapped them and no difference.
When I rebuild the engine, I got a different head for my N51 engine, had to change the original because the intake froze and chain broke. Did valve job on the replacement head. But now I am questioning the pressure of the oil to turn the Vanos gear. It is fine on the exhaust it seems. Something is not working right in the intake side of the Vanos. I don't remember if there were ridges on the cam cap by the oil seal rings which are new from the dealer. I used the old exhaust cam for the new head and it is fine no codes. Used the intake camshaft that came with the head for intake.
I don't know what to do next, short of buying another head and making sure the seal rings are going to be good. I have tested everything else including the oil filter and O-rings and Liquid Molly oil change.
Any advice would really be appreciated