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      03-04-2012, 11:19 PM   #19
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bigjae1976's Avatar

Drives: 11 E90 M3 Individual
Join Date: Mar 2006
Location: Wichita, KS

iTrader: (14)

Garage List
2004 BMW M3  [4.50]
2011 BMW E90 M3  [5.00]
2013 BMW 328i  [5.00]
Originally Posted by M3roar View Post
Yeah, Id rather it running rich than too lean... I'm getting some boost gauges installed .... I might at that point custom make some pulleys for different levels of boost and find one that fits the bill for rich/lean ratio...
I found out that part my problem was the 4 screws which hold the compressor onto the manifold were coming loose. There is RTV which acts as a gasket. I think the RTV was basically preventing a massive vacuum leak...which my time at the track caused it to just a smoke test revealed. I had to pull the entire manifold/compressor assembly. Then clean and apply RTV to the surfaces and loctite the bolts.

What I learned is a vacuum leak could cause your car to run rich. Unmetered air causes the computer to increase the fuel trims and start dumping fuel...causing your car to run pig rich. I believe that at idle, where my car ran like crap, there would be a leak from the manifold/compressor joint. Then when you get under boost, it would seal the joint, kind of like suction. So the computer would increase the fuel trims at idle as a part of adaptation, thus, the car would run rich under boost due to no unmetered air and the joint sealing. I'm guessing because I didn't spend as much time under boost as I did under vacuum that the DME would not adapt itself. That would also explain my mix of rich and lean codes.

You can check 2 of the top'll have to pull the assembly to get the bottom bolts. Or have a triple jointed wrist. Wouldn't hurt to rule it out.

Oh yeah...hope you sell your wheels.
2015 F34 328iX GT Glacier Silver
2011 E90 M3 Monte Carlo Blue
2004 E46 M3 Imola Red