SO the latest update on my Cyl4 misfire is:
Swapped coil packs on Cyl 4 & 6 - result was cyl misfire codes for cyl 4, cyl 2 and non-specified cyl.
Checked cyl 4 plug and gap was about 0.5mm too big. Adjusted & cleaned plug - result was back to only cyl 2 code and misfire not as bad as previously.
Took out and cleaned cyl 5 & 6 coils (no tracking evident). Took out and cleaned cyl 5 & 6 plugs - minor gap adjustment, about 0.2mm - result was no noticeable difference.
Cyl4 excessive plug gap the major contribution to the misfire, but with that gone a previously masked lesser issue on Cyl 2 is showing up.
Looks like I now need to get to the rear bank of cylinders and check plugs/coils, on Cyl 2 at least.
Interesting that after swapping C4 & 6 coils and doing nothing else I started getting a Cyl 2 error code as well as Cyl4. I assume that Cyl4 was worst to start with and maybe therefore most "noticeable" to the ECU and am wondering if the big spark gap has maybe weakened the coil pack (could larger gap has increased stress on the coil pack, or would it just weaken the spark??) so that when I moved the pack I no longer had the weak plug and coil together so the Cyl2 fault started to be noticeable. However there were no visible signed of tracking / breakdown or damage on any of the coils.
Will have to find the thread that talks through taking the throttle body/intake plenum off so I can check out the rear cylinder bank plugs and coils next weekend.
07 3.2 Q4 SV Brera alfa red --- previously '99 156 2.5 V6 for 9.5 years
Last edited by Burnsy; 15-09-13 at 23:07.