1986 v6 135 Mercury missing randomly on one cylinder

[UKMike]

Hi all,

Can anyone advise on this issue I'm having, I have a v6 135 Mercury that misses 3 or 4 sparks randomly, I know this because I have tested with a spark light, can anyone advise what the cause would be?

Already put new coils, plugs and leads on her, and swapped them around to make sure none are faulty.

Thanks in advance.

UKMike

 

[faztbullet]

If you raise the rpm a little does problem go away??

 

[UKMike]

Hi Faztbullet,

Yes it seems to run fine over 1000 rpms although do get a little judder every know and then.

Br
UKMike

 

[UKMike]

Just to help on the analysis, it is only on the middle starboard side piston where the spark seems to fail randomly although the plug in the top port piston is also slightly oily sometimes although not enough to worry about and is normally burning just right. It has to be a spark issue, here is a link and you can hear it running and see what it does.
https://onedrive.live.com/?cid=1C3B25C66558894D&id=1c3b25c66558894d!548&v=3

Br
UKMike

 

[faztbullet]

Get a DVA adapter and check th output to that coil or swap the 2 switchboxes around and see if problem moves with that box...