E46Fanatics - View Single Post - Rough idle cold start CEL on 325XI
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Old 12-19-2012, 03:51 PM   #10
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Join Date: Aug 2011
Location: Reading, Pennsylvania
Posts: 814
My Ride: 03 325xi, 01 325xi
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Question, when you changed the spark plugs, you removed the coils, was there any oil on the bottom of any of the coils where they fit onto the spark plugs? Was there oil on any of the spark plugs? Was there any oil in any of the spark plug wells? If the answer to any or all of the previous is yes, then you have first got to replace the valve cover gasket set. The "o-rings" that seal the spark plug wells get hard and crack long before the outer valve cover gasket does. The coils do not like oil and it will cause a misfire. If any of the coils did have oil on their boots (and by the way, did you replace the coil boots when you changed the spark plugs, you should have), you may well have to replace that coil or coils. Bosch coils are fine to use. If you tore any of the coil boots when pulling off the spark plugs, you can have spark leakage to the spark plug well that will also give a misfire. So, re inspect the boots and I would recommend replacing the boots. When putting the new boots on and before pushing onto spark plugs, put a little di-electric grease on the inside of the boots so that they come off the plugs easier (doesn't have to be a lot, just a thin coating). If all that checks out and you still have just a Mis-fire on one cylinder, it could be several other things including the DISA Valve. When the DISA Valve is broken, too much or too little air can get into the intake runners and cause poor idle sometimes, and other times idle fine, and it will usually throw random mis-fires across all 6 cylinders. When you had the code(s) read, did you have them reset? If not, have them read again and reset, do your repairs and look for the CEL/SES light to come back on and then have codes read again.
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