My '91 320 E36 started to misfire a while back. It's really obvious at tickover and not so obvious at full power on high revs. (but no warning light on dash)
So, I pulled all 6 spark plugs and number 3 was black. The rest were a fine "tan" colour. (And I found I've got the leaking oil problem while I was in there! New gaskets are next on my list to do...)
So, could it be a bad ignition coil? My guess is a leaky/faulty injector. If there is a chance it's the ignition then I can buy a new one for about a third of the price of an injector.
Is there any easy way to test which bit is faulty? I can swap ignition coils over easily and see if the "black" moves with it, but I imagine it takes quite a while to get black enough to see? Any estimate on how many miles?
To move the injector would be a bit more work having to remove the whole fuel rail etc...
Thanks for any ideas!