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Old 05-16-2012, 09:58 AM   #15
jdstrickland
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Join Date: Apr 2010
Location: Murrieta, CA
Posts: 6,698
My Ride: '94 325iC & '00 323i
Quote:
Originally Posted by rfbmwfan View Post
Hey guys, I'm stumped on this. Out of the blue on my way home the other night, car starts missing. Next day I switch coil packs, plugs, fuel injectors, and no matter what the miss stays on cylinder 5. So I hook up my bmw software to diagnose. Im getting DME code 1F ignition activation, along with p0305. The miss only starts when the car is warmed up and running for a while.

When I clear the code, the car runs fine for about a minute, then starts missing again.
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You have a SINGLE CYLINDER MISFIRE, you have to concentrate on that single cylinder. All of the other stuff you are doing 1.) confuses the issue, and 2.) will cause global problems across all cylinders. You need to go back and look at stuff that is unique to the cylinder that is giving trouble. Swap the #5 coil with another coil AND NOTHING ELSE, and see if the problem follows or not, if the problem follows then continue looking at the coil. Do not introduce new parts, and ESPECIALLY do not introduce used parts, because if the new part is no better than the onen it replaces, then you will be chasing your tail. You have no misfires on the other cylinders, so all of the other coils work. Put the currrent #5 coil someplace else and put that coil on #5. If #5 remains the problem, then look to the plug on #5, and then start looking at the injector. All of the other injectors work, so swap the injector from another cylinder into 5, and put the #5 injector into that cylinder. See if the problem stays on 5 or moves.

The idea is that you are doing 4 or 5 things at the same time, and you need to do one thing and see if the problem follows that action or stays in place. If you move the external parts -- coil, injector, plugs -- from 5 to a working cylinder, and the parts from the working cylinder to 5, and the problem remains on 5 through all of this, then you have an internal problem.

Your car has already isolated the problem to a single cylinder, there is no point in looking at stuff that covers all of the cylinders that are not having a problem.
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