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Old 09-28-2012, 09:08 PM   #29
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Join Date: Aug 2011
Location: Reading, Pennsylvania
Posts: 814
My Ride: 03 325xi, 01 325xi
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Idle Control Valve was checked and cleaned at same time Throttle Body was Cleaned, when I replaced Oil Separator Valve and its 4 hoses, though not saying it isn't bad. Total of 4 sensors on the XIs, 2 pre-cat and 2 post-cat. Definitely the pre-cat ones were bad, and after replacing them the random misfires of all cylinders went away (been a week now since replacing and clearing codes). However, after 3 days, the codes I mentioned before came back, so: 1) I'm thinking the post-cat O2 Sensors need to be replaced, 2) the DISA should at least be checked. The pre-cat O2 Sensors if not working correctly will lean the fuel/air mixture out and can cause random misfires.
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