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      02-13-2018, 12:28 AM   #8

Drives: 2008 BMW 335i sedan
Join Date: Aug 2014
Location: Russellville, AR

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2008 BMW 335i  [0.00]
Originally Posted by eyehategod View Post
Thanks, I was thinking this might be the issue. I'm going to order another spark plug just in case I messed up the one in cylinder 4. The process of getting to the plugs took so long for a noob like myself, I don't want to tear everything apart more than 1 time (already upset with myself that I've gotta do it again).

While I was at it, I was going to buy come MAF cleaner. I changed my oil at the same time, and I think I read somewhere that the filter can get oil onto the MAF somehow?

BTW: I didn't clean out any of the carbon (I think it was carbon, definitely not oil) that I found in the cylinders. Should I have cleaned this out while changing plugs, or is this normal?
The N55 and earlier N54 engines in the 335i do not have a MAF (Mass Air Flow) sensor. The N54 N55 have a MAP (Manifold Absolute Pressure) sensor. These sensors aren't generally as sensitive to oil in the intake tract as hot wire MAF sensors. Regardless of what sensor you have, changing your engine oil would have absolutely no effect on it. If you have an oiled gauze air filter like a K&N, putting too much oil on the air filter has been reported to contaminate MAF sensors on other vehicles. But this has nothing to do with changing your engine oil.

The carbon inside your cylinders is most likely from oil that has burned up during combustion leaving behind the carbon deposits. The most common source of this oil on our engines is the Positive Crankcase Ventilation (PCV) system that dumps crankcase oil vapor into the intake ports. This is why people install oil catch cans (OCC) on the PCV system.