Hey guys back with my bad misfire again, ran very well for a little while but same symptoms again. Rough idle, rough to 2500 rpm. Seems to be Running rich. All the usual suspects have been replaced almost all new parts on my motor. Fuel pressure good, 180 psi across all cylinders. P0300 code, already tried easy stuff like unplug the MAF, etc. My injectors are the upgraded delphi mpfi unit, but they have 200k miles, could one be sticking? My trans is going out, can a bad torque converter cause a misfire? A while back i took a video of my valves, #6 looked weird, i shrugged it off at the time as my motor ran great. #6 was the problem last time, plug cracked the jacket, new plug bam running great and did till like a week ago. If anyone has ideas i greatly appreciate them.


Any ideas on what the silver is? Broken seat? Debris?

 

Piston?? Try taking photos through the spark plug hole. If valve or valve seat was damaged then no compression at all.

 

Well went and got the loaner Borescope(didn't have compression tester) here's cylinder 6 and the adjacent cylinder 4, not looking good imo my buddy thinks its carbon deposits on the piston but im thinking it looks like pitting, possibly from detonation? From what i could see of the valves they looked ok, any other ideas why my piston might look like this and would a damaged piston make it run this bad? Thanks

Forgive my poor pics, couldnt offload pictures from the Borescope...


Up close on #6 piston, walls dont look too bad but the piston looks a little beat up to me.

Zoomed out on #6

Cyilnder 4, looks pretty good imo

 

I dont know much, but I dont think it looks good. Did you get the crud out?

I think the build up or crud may have cause an imperfection in the seating area of the piston, or maybe be causing a small gap, so the combustion maybe be off.

 

Welp, finally got another truck and decided to find out what was wrong with the ol blazer. For anyone that was wondering Turned out to be the #6 intake valve not sealing properly, looks like pitting on the valve itself. So for now she sits, might part it out... Anyone want to make me parts offers?

 

Glad you figured it out.

Feel free to create a thread in the For Sale / Trade section for that kind of discussion.