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Old 01-24-2013, 03:18 PM   #4
Dare32
Registered User
 
Join Date: Apr 2012
Location: US
Posts: 32
My Ride: X5, 325Xi
Yes, I found what was wrong...

After almost 6 months of searching, reading, testing, I found small leak between cylinder 3 and cylinder 4. So the leak is from one cylinder to another, no other systems involved so I had no problems with oil, coolant or leak outside.
It was internal leak only and that was determined with the "leak down" test. At this point there is no way to see inside and figure out where is leaking but it's one of the 2 things. Or is cracked head or blown gasket. Many will say gaskets are not going bad on these cars as they are layered metal plates, but that was exactly the reason for this fault. Take a look at the photos. I had to take the head off, resurface it, replace head gasket and other parts when I was at it.
Car is now like new, but taking those exhaust nuts off was pain in the *ss.

http://db.tt/dQ2gHeeL
http://db.tt/kKuRT3Jj

I hope this helps, and by the way the original issue, before it started to misfire was O2 Sensor PreCat bank2. It was too slow and once replaced secondary air would get ready on first trial.

Good Luck
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