I know a few threads have touched on this but I couldn't seemt to find them (damn search engine).

I've mentioned a few times that I've had internittent misfiring with my Comptech SC/E-manage (8lbs) system. Seems that under certain conditions (and I never did nail down the exact details) the engine would misfire at around 7000 or up at 8500-9000.

I pulled the plugs a few times and set different gaps based on what we have discussed here but nothing seemed to make a difference.

So I replaced the plugs. Can't find Densos anywhere here so I bought NGK Iridium BKR7EIX-11. I checked the gaps before install (expecting 0.032) and my 0.035 just slid between them with room to spare. I didn't bother measuring the actual gap but checked them all and they were pretty much the same.

So I installed them and it runs fine. No more misfire.

They must be at 0.039-0.040 but as it's running nicely I ain't touching it.

So what was wrong with the old plugs? Too close a gap? Or are they damaged in some way? The system runs pretty rich and there was quite a lot of black around the skirt of the plug, but the electrodes looked pretty good. What deteriorates about a plugs? I know the tips can burn off. I know they can foul, but I would think you could just clean them up.

 

not using S/C...but mugen ECU, similarly took out a set of NGK iridiums ~ 5000km old with 1.0mm gap...(also very black around the skirts) and replaced with Denso iridiums - kept the gap setting as supplied at 0.6- 0.7mm out of the box, and the engine had new life...