thank you for this excellent thread on the 6-cylinder-misfire thing. Although many people seem to experience this problem, there is only litte to be found on the web about it that makes sense.
I want to add something, though:
After I bought my BMW 6 months ago, it was not running very well, only on 5 cylinders most of the time.
My BMW had the following error codes: Misfires on Cyl. 4, Cylinder cut-off due to misfires, Lambda values out of mearuement range, fuel injection at maximum range, intake cam shaft sensor broken.
I first replaced the camshaft sensor and all the hoses of the crank shaft housing valve and the valve itself. The lambda, fuel injection and cam shaft sensor errors were solved, the misfire (though without the cut-off of the cylinder no. 4) persisted.
I replaced many parts, like ignition coils and plugs, spark plugs, wiring from DME to ignition coils and some faulty temperature sensors. I cross-changed ignition coils, injectors and so on. I cleaned the injectors in an ultra sonic cleaner. I checked the cam shafts for abnormal pitting or wear.
Before opening the engine itself, I wanted to make sure there is no other, cheaper source for the misfire. So I found myself a company that checks and repairs DME-units. And guess what, they told me that the circuit/amplifier/mosfet is broken that does control the injector of cylinder 4....unfortunately, repairing it will cost about 600 $ :-/
So, if the misfire is only on one cylinder and does not move to another one when cross-changing parts between cylinders, make sure you find someone to check your DME.
I read about so many people replacing their hydros (are the called like that) or worse for 1000s of dollars with no effect...better make sure the DME is working properly.
Oliver aka Tomcat0815
Last edited by Tomcat0815; 02-17-2011 at 12:20 PM.