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    FIXED/ BMW /318i E46/2002/N42B20A/WBAAY72030KJ Archived Message

    Posted by Christopher Taylor on August 7, 2007, 10:47 am, in reply to "Re: BMW /318i E46/2002/N42B20A/WBAAY72030KJ"

    The hot idle surge was caused by the oil filler cap. It is hard to describe the design of this BMW cap but essentially it is supposed to prevent the cap from going missing and is fixed to a pivoting retainer that is keyed to the engine rocker cover. Now if you are a little heavy handed it is possible to unclip it so that on refitting it does not seal. It is not that obvious a fault and easily missed. Apparently if fitted badly enough you can hear the leak and the engine will misfire and store a code for mixture adaption or something like that but with my vehicle the leak was not that easy.
    Many thanks to all who replied especially two Irish technicians Alan Kane who hit the nail on the head and Bobby Madigan who gave me an interesting insight into the design and operation of this unusual engine. Both these men are a credit to this forum not just for their knowledge but also their generosity when helping out.
    Other faults known to this model are the air box rubbing through on the aircon pulley and a driveability issue experienced as poor performance when accelerating in "acceleration lane" situations which is cured with an ECU software update.

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