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Old 11-24-2011, 07:03 AM
cn90 cn90 is offline
Officially Welcomed to the 'Fest
Location: Omaha NE
Join Date: Mar 2006
Posts: 14,365
Mein Auto: 1998 528i 5-sp 140K+
Carbon Buildup in combustion chamber has many many causes. The bottom line is:

- Gasoline leaves behind a tiny of carbon when burned. Do this experiment outside on your driveway: burn a small amount of gasoline, maybe 10-20cc in a small metal can, and see what is left behind.

- Oil leaves behind a lot of carbon when burned. Do the same experiment using 10-20cc oil.
Don't tell the enviromentalists you are doing this (j/k)!


Common causes:

1. Cheap Gas, This is a Must-Read written by Larry Carley, "Watch Out for Bad Gasoline":

2. Engine Oil somehow gets into the combustion chamber:
- Loose piston rings (unusual before 200K for M52/M54 engines)
- Loose valve guides (unusual before 200K for M52/M54 engines)
- Clogged CCV ---> #1 cause in M52/M54 engines
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