misfiring - what's the possible cause???

[c-square]

My friend's M54B25 showed the message "misfiring" in cylinder 1,2 and 5 when the modic was plugged into it. What could possibly be the cause of the misfiring? Is it an indication of failing Vanos? The mech said that it is just a simple fix, ie merely perform a reset. Somehow we were not so convinced. Gurus out there, care to share your thoughts?

 

[E34EuroTouring]

For M54 engine, double vanos. Its unlikely the vanos unit. More like the coils over the plug. What is the mileage of the car and condition of the engine ?. Has it overheated before ?.

Are the spark plugs good or very foul already ?.

Reseting the ECU would be a good start. But make sure the coils and the wiring to the coils are ok . If they spark when one sprays a water mist, then you have current lead and the wiring needs replacement. Injectors could not be an issue for 1999 car. Tell us more clues on its behaviour. Idling ok ?. Exhaust fumes ok, not white fumes or mixed white blue fumes, or too rich petrol smell ?.