Which cylinder is which, P306 misfire on cyl 6.

[rG-tom]

Hey guys,

I've got a "misfire on Cylinder 6 (P306) that comes up if i leave the car to idle when cold. If i drive away immediately from starting, it never comes up, and if i reset the code using an ODB2 reader then it goes away and doesn't come back unless i leave the car idling for >30 seconds when cold.

The car is also not perfect even when warm, big flat spot around 1800rpm etc and sounds a little rough.

I change the coil pack on what i thought was the 6 cylinder, and the car DID seem a lot better after, but a week later it's as bad as ever if not worse! Which one is cylinder 6? I have taken it to be the one closest to "firewall"...is this right? If not, it may have been just placebo! I have an m54b30 engined 2003 Z4 3.0i

Any help is appreciated.

Thanks,

Tom.

 

[mmm-five]

#1 nearest the front bumper
#6 closest to the driver

Although I had a code saying misfire on #4 and it was actually #1 that had the issue.

 

[rG-tom]

#1 nearest the front bumper
#6 closest to the driver

Although I had a code saying misfire on #4 and it was actually #1 that had the issue.

Thanks for that....that sounds brilliant though, how did you diagnose it in the end and was it the coilpack?

 

[mmm-five]

Thanks for that....that sounds brilliant though, how did you diagnose it in the end and was it the coilpack?

Trial & error as we kept swapping out plugs, coils, etc. on #4 and it didn't seem to make any difference.

The only thing that made any difference was putting a coil from #2, #3, #5 or #6 onto #1. We'd reset the codes and it would be fine. If we swapped them back (remember, we didn't touch #4 as we thought it was faulty) then the error on #4 came back.

We did this for about an hour, put them all back where they were originally and then put a spare coil pack on #1 and all was fine. We then double-checked by removing the spare coil pack and putting the original back into #1 and this time it didn't bring up any error.

We started & stopped the car a couple of times, took it for a short drive, and everything was still working.

So all I can assume is there was either a dodgy sensor, or the fiddling had put something back in the slightly different position that made it work.

That was about 60k miles ago now and despite carrying a spare coil just in case, it's never missed a beat - other than when I had that useless* Simota intake on.


* supposedly now fixed so that the car doesn't cut out when you floor it down a motorway slip road