Misfire readings on cylinder 8
 

So I’m picking up misfire readings on cylinder 8 watching misfire counter on snap-on scanner. I’ve swapped coil and wire to different cylinder but still showing misfire. Pulled old plug and it was black on tip. Added new colder plug and week later it’s black as well. What could be the issue? I have bigger injectors and Ecs supercharger plus cam

Would think injector based on what you did so far. Likely leaking. Might see in a pressure test (pressure dropping gradual after pump prime). A compression test would not hurt either.

Ok. Would you recommend i swap injector to different cylinder first or compression test? Which is quicker?

Not sure if your tagged when i hit quote on reply

Can anyone else chime in on this question please

check for a cracked plug. some are hard to see. but will cause a misfire, happened to me on the dyno.

So this occurred with old plugs in it and then i changed to a colder plug and it still shows a misfire on cylinder 8. I pulled that plug as well a week later and it was black as well on the tip. Everything I’m reading leads up to a possible injector leaking but not sure.

swap the injector to the #1 cylinder and see if it does the same thing to the #1 plug

I’m gonna do that but didn’t realize how big of a job it is lol. Do you think that would be the only issue or do a compression test on that cylinder as well?

Needs a rebuild. There is a chance that hard to get to plug got cracked, start with putting in a new plug before pulling the engine for a rebuild. And black on the plugs might want a hotter plug not colder, but that won't fix it here.

Could be a valve spring or ring land.
First step would be a compression test. Then if ok remove the valve cover.
Swapping injectors is not a huge job but I doubt this is the problem.

swap the coil, and plug wire to a difference cylinder to see if the misfire moves. compression test is quick and easy. test all of the cylinders on that bank it will tell you what normal compression should be. Injector swap would be the last thing I do if all else checks ok. If compression is low pull the valve cover look for broken spring or loose rockers missing trunnion needles.

I’ve done swapped coil and wire and it still showed a misfire on 8. Will do compression test next. Would i not hear a ticking if rocker or spring was loose?

So we’ve done compression test and number 8 is about 20 down from the rest of cylinders. Readings were in the 180s on all but cylinder 8 which read in the 160s. They did a blow by and it came back perfect. Spring and lifter look fine as well. They also swapped injectors but misfire counter still shows misfire on 8 ����*♂️ Anything else y’all can recommend checking?