1) Change the air filters. Cleaned them since it came with k&n filters. I didnt oil them!
Then you haven't really cleaned them properly. The oil is designed to help catch dirt particles. I suggest you oil them, and then LET THEM DRY FOR A COUPLE OF DAYS before you reinstall. Most people over oil them and the excess oil can foul the MAF's.
1. change the fuel filter
2. Replace the K&N filters with PAPER FILTERS
3. Run the MAF/Fuel flow test (look in the FAQ post that is stickied at the top of the page
I suspect the mechanic was seeing whacked out fuel trim numbers, and hence wanted to adjust them- he is ignorant and failed to understand that it is bad mafs (ie fouled mafs) that CAUSES fuel trims to distort...
'12 Alpina B7 SWB Alpina Blue/Black (On Order)
'11 1M Coupe Alpine White/Black
'08 M6 Coupe Stratus/Black
'03 M5 Sedan Imola Red/Black (gone, but not forgotten)
'93 M5 Sedan (3.6) Sterling Silver/Black
'11 550i Dark Graphite/Oyster-Black (wife's car)
Past: '11 M3 Coupe | '08 M5 Sedan | '10 M3 Coupe | '07 M6 Coupe | '07 Z4 M Coupe | '04 M3 Coupe | '02 M5 Sedan | '95 M3 Coupe -- x2
So just installed the plugs today and finally the car is perfect! Strangely, I was expecting a badly fouled plug but I didnt find any. Only one that slightly had a darker brown color than the rest. Phew, I was ready to look for vacuum leaks, changing the MAFs and CPS sensors, O2 sensors etc.
glad to hear camlob! The DME does take a lot into consideration. Replacing any of the parts above is a great idea depending on mileage. I strongly suggest replacing the oiled air filters with plain paper ones along with new GENUINE Bosch MAFs. The oil is notorious for coating the MAF sensors and making them less efficient. Yours are most likely contaminated and causing power/mpg loss as well. The contamination can only be partially removed with cleaning solution. Consider some of it baked on permanently.
Notice also from the .pdf you linked that pre AND post cat O2's affect the fuel mappings as well. I consider it a detriment that your car is missing its cats. How many O2 sensors are installed? 0, 2, or all 4? Also how many miles/kilometers are on this car?
Tim - 4 O2 sensors are installed. The car has 23k miles on it. Yeah I think MAFs will have to be changed. Can you suggest any vendor that sells them at a reasonable price? I read that bimmerzone sells them cheap.
So my nirvana was shortlived. Just today I experienced the richness again, sigh. So I will be ordering the MAFs and O2 sensors. I dont see the logic on why cam position sensors will affect fuel trim? Should I order them anyway?