Fuel soaked spark plug #5 cylinder

Silvercat

Member
Messages
1,166
Hi All, my 2009 QP 4.7 developed a misfire a couple of weeks back on the #5 cylinder. Managed to remove the ignitor coil and the NGK plug today and I was surprised to find a black/dark brown plug end as if it had been burnt and it was wet (fuel!) when I took it out of the cylinder. It's not soot but it looks like it's been running hot judging by the colour. I have ordered a new plug and ignitor coil but is there a possibility that the injector is faulty and pushing too much fuel into the cylinder? I need to drive it 6p miles yo the nearest Mas garage to get it double checked; just hope it won't breakdown on the way. Will a new plug get me by for now?
 

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SJX

Junior Member
Messages
81
Most likely coil pack thats at fault. Alot of messing but you could pull another plug and check it as comparision. How did you establish it was cylinder 5, if it was from a code reader then just fit new coil pack and plug, and see if throws up any fault codes after original cleared. Obviously check connections are snug and clean.
 

conaero

Forum Owner
Messages
34,593
Most likely coil pack thats at fault. Alot of messing but you could pull another plug and check it as comparision. How did you establish it was cylinder 5, if it was from a code reader then just fit new coil pack and plug, and see if throws up any fault codes after original cleared. Obviously check connections are snug and clean.

This. The coil pack fail then the fuel entering the cylinder soaks the plug and voila!
 

Swedish Paul

Member
Messages
1,807
Is there any recommendation on routine change of coil packs? I recall there are on Aston Martin, 80,000 miles as i recall.
 

Swedish Paul

Member
Messages
1,807
I had the same, was just the spark plug gone kaput. I got the slow down light as unburnt fuel was hitting the cats
 

Silvercat

Member
Messages
1,166
I bought a replacement ignitor coil and spark plug, swapped them out and now my QP is purring once again like a big cat! All done for £112. Very happy. I am going to carry a spare coil and plug just in case it happens again. I am told that once one ignitor coil fails then the rest are probably not far behind. I also bought a thirty quid code reader and it's brilliant, picked up the fault on #5 cylinder straight away. Access was a bit tricky but just unbolting a few things to clear the way worked perfectly. So thanks everyone for pointing me in the right direction...much appreciated.