In general, when we look at BMW datalogs, we first look at individual cylinder timing correction under full throttle. Timing correction under part throttle would be very normal. Under load though, you want to see minimal corrections in the cylinders, but small corrections in 1-3 would be normal. Consistent corrections in 3+ cylinders or corrections that re-increment would indicate the mapping is too aggressive for the mechanical condition of the car.
Common Mechanical Ailments:
- Bad spark plugs/coilpacks
- Carbon build up on intake valves
- Bad tank of fuel or low octane fuel