So i had a pretty bad misfire going on and i pulled the plugs to do a compression check and i think i found the culprit of the misfirings.

Plugs number 6 and 8 were both in the condition seen in the picture. For those who cant tell, the ground electrode has contacted the center electrode. I do have an MSD 6a box and an MSD coil, oem style plug wires, cap rotor distributor, etc. all brand new. The plugs are autolite single platinums. Why would this be on 2 out of 8 plugs? are 6 and 8 connected in some way by design(as in one is on compression while the other on exhaust simoultaneously) 1-8-4-3-6-5-7-2... i'm going to try out 6 new plugs and put 2 old ones in 6 & 8. i just bought some accel shorty header plugs and dont want to let the engine eat them. What is goign on?????

thanks,
boldguy

 

maybe you got so much carbon built up on the pistons that they are pulverizing the plug tip. get some sea foam and run thrugh the vac hose while running..

 

So i fed a spark plug wire, that i cut the tip off of, down the spark plug hole in #6 and it came out pretty black. Then i put just 1 old (ok shape) into #6 and cranked the motor to see if i had "mechanical damage" and the plug came out looking the way it went in. I put two old ones in to #6and 8 and the rest are the new accel's and i ran some seafoam through the cruise control vac hose, and immediately noticed that it was running awesome!. Ill see how #'s 6 & 8 look tomorrow and if they are fine, then ill just throw the new ones in and call it a day. Maybe i can pass smog now...Hell yes i can!

 

I don't really see any build up on the plug... Gonna place my bets on foreign object found its way into the cylinder or... and this is more likely piston slapped at TDC. It is rare but as tight as these flat top pistons can be... IF it might have detonated at exactly the right time and shifted in exactly the right direction... I could see this happenening with no other symptoms. You might be able to see if some of the other plugs have a light glaze on them. The biggest hint is the ground was hit but it wasn't folded over the firing eletrode. Light impact probably at speed or accelerating.

I know it's a long shot but stranger things have happened.

 

I put the old ones in numbers 6 and 8 and pulled them out after driving it for a while and they were fine. So i put the accel's in and the car has been running fine ever since. They are flat top hypereutectics if that makes a difference... but i dont know what in the name of god would have just showed up inside the cylinder one day; it crossed my mind but i dont think the chances are that high...

 

So i pulled the plugs, namely 6 and 8, and they were fine attached is a pic of number 8. So i did a compression check on all 8 and they all read 200 psi steady and held. is that normal?? the engine is fairly new ~20k miles...


I disconnected the MSD ignition box and it kind of smoothed out the drivability, but still a misfire here and there...