E53 2006 4.8is rough idle cold start - help required

[Hugo74]

Hi All,
I own a X5 2006 4.8 is with 195000km (N62 V8 engine double Vanos).
I have a rough idle at cold start which go away after 40 seconds, but when i drive the car, the engine sound is weird and the behavior/power of my BMW is not like before... yes... by before I mean the following events;

Got oil level check light some weeks ago, some weeks after doing my oil service... brought back to the workshop, they found 2 major oil leaks (not seen at time of service... anyway) + lack of coolant (coolant expansion tank cracked). Note; I did not get any light on my dash board for the coolant.
Got my cylinder head cover gaskets and the upper timing gaskets replaced (both banks), coolant expansion tank, thermostat and some hoses replaced.
Got back the car...the first morning at cold start I had a rough idle, but the ignition was correct (cranking time very short), I have the rough idle after 3-4 seconds, after 40 secs approx, my rpms go up 1000 and come back to 500-600... no more rough idle then.
But the engine is not ''singing'' like usual, the behavior is not like before, no power, my car is now a lemon.

Back again to the workshop to find the root cause and to fix it;
- Vanos codes 2A84 and 2A89
- Misfiring codes but did not come back after deleting faults codes and start again the car when warmed-up
- No coil/sparkplug fault code
- No alternator/battery fault code
- camshaft positionning found to be correct after adaptation programming.
- we replaced both Vanos solenoids on bank 2: No positiv result
- We replaced 8 injectors: No positiv result

Questions:
- During the gasket replacement, according to you, what could happen? sensor broken or wrongly placed, damage on Vanos or eccentric/camshafts?
- Since I ran with no coolant for a while, did I burn some gaskets which are now allowing some coolant entering into cylinders and cause those misfiring?

I already read many threads about misfiring at cold start and rough idle like mine, but there were so many possible root causes...
I'm lost, my mechanic seems to be as well...
any help from you guys will be appreciated

Thank you

[TerminatorX5]

it is hard to suggest something when you have a professional mechanic is by your side... If i were doing it myself, i would have checked all the connections, especially MAF, i would look to see if there is no vacuum leak, like a displaced tubing... the codes that you are getting, could be secondary to the main issue, that is probably a misplaced connector...

can you retrace your (your mechanic's) steps to see if every wire is plugged in without any loose wires/plugs...

[Hugo74]

Hi Terminator X5.
Thank you for your suggestion, the problem is that I do not know if my mechanic did duly follow BMW workshop manual...
I did attend previous work like injectors and solenoids replacement, but I had to take day off to do so, now I'm at work waiting for any finding from his side...
about the MAF, I did inspect it myself... first thing I did and the second thing I removed the main Air intake throttle to check if it was not dirty or blocked... clean and functionnal ((forgot to mention it before sorry)

To come back to the BMW manual, the procedure to follow to remove cylinder head and upper timing cover gaskets is simple but shall be followed, especially when we talk about bolting screws in a specific order with a specific torq wrench. He gave him those instructions, is he going to follow them... still I'm not behind his back to check! and I'm really worry about he is going to tell me after his todays investigation.

what do you think about coolant leaking option? impossible?

thank you again
Cheers

[tmv]

Originally Posted by Hugo74

...
Questions:
- During the gasket replacement, according to you, what could happen? sensor broken or wrongly placed, damage on Vanos or eccentric/camshafts?
- Since I ran with no coolant for a while, did I burn some gaskets which are now allowing some coolant entering into cylinders and cause those misfiring?
...

You weren't driving with no coolant. It was just low, but not to the point that triggers the message on the cluster. There would be all kind of warning and even engine shut down if you have NO coolant.
Is your mechanic a BMW one or just a regular one? He should have BMW diagnostic tools to check it for you, namely INPA and DIS.
I would also make sure the gasket got seated correctly and the bolts properly torqued to spec to get the perfect seal.
Good Luck.

[Hugo74]

just got a call from the workshop...
they did change both Vanos adjustment units on Bank 2 and it seems that this fixed the problem.
I'm happy and frustrated by the same... they probably re-installed covers and sensors correctly this time and they gonna charge me two brand new Vanos....

I will get back the car this evening... I will let you know... but this will be probably more a commercial issue thread now than a tehcnical one...

Cheers and thank you again for your answers guys