2 of 8 spark plugs black
2 of 8 spark plugs black Ok so plugs 2 4 6 8 are all the same color as well as 1 and 3 but 5 and 7 are black. What could cause this? Injectors were tested fine so were the coil packs. I replaced the wires when I put new plugs in so they're new this is the 3rd set of plugs I put in that side and always 5 and 7 are black... What could cause this? That would explain why they could never get the tune right... Ps: o2s were changed as well second time. Everything was changed and checked the 2nd time now it happened a third time. I'm pretty much at a loss. Any ideas?
Ok so plugs 2 4 6 8 are all the same color as well as 1 and 3 but 5 and 7 are black. What could cause this? Injectors were tested fine so were the coil packs. I replaced the wires when I put new plugs in so they're new this is the 3rd set of plugs I put in that side and always 5 and 7 are black... What could cause this? That would explain why they could never get the tune right... Ps: o2s were changed as well second time. Everything was changed and checked the 2nd time now it happened a third time. I'm pretty much at a loss. Any ideas?
Car down on power ? Do a leakdown
Trending Topics
Black could be from oil fouling or from rich mixture.
Possible issue with incomplete combustion or oil control.
Hopefully the guides are good on the heads, but guides aren't known for wearing much unless you are running a pretty high lift cam with stock type rockers.
Could be an ignition or fuel issue.
Possible issue with incomplete combustion or oil control.
Hopefully the guides are good on the heads, but guides aren't known for wearing much unless you are running a pretty high lift cam with stock type rockers.
Could be an ignition or fuel issue.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo The shop told me looks like a carbon from not burning right because the other 6 also have oil on the threads but look fine. But why would only 5 and 7 have issues? Everything is new and was checked twice. Could something in the tune cause that? Or would it be all of that bank?
The shop told me looks like a carbon from not burning right because the other 6 also have oil on the threads but look fine. But why would only 5 and 7 have issues? Everything is new and was checked twice. Could something in the tune cause that? Or would it be all of that bank?
TECH Fanatic
Joined: Mar 2014
Posts: 1,266
Likes: 165
Check the easy stuff first. Move those 2 injectors to different spots just to rule them out. If that don,t work move those 2 coils. If that don't work check the harness and make sure all the pins are in place. Sometimes they can push out while plugging them together. Then check and see if you don;t have the rockers too tight not letting the intake valves close completely. Hopefully you don't have a couple bad lifters.
TECH Fanatic
Joined: Mar 2014
Posts: 1,266
Likes: 165
I'm not sure what ignition you have but is there any chance you have individual cylinder timing, and those 2 holes have the timing reduced? Just trying to through out there anything I can think of. Also make sure you don't have both coil harnesses swapped from side to side. Motor will still seem to run fine. Won't break up till you hit like 6000rpm.
I switched coils and injectors and still runs like crap. I also checked the wire harness and everything seems fine. As far as I know you can only put the coil on one way where the 4 connect so should br on the right side of the car and as for individual timing I'm not sure what the tuner did its the stock 411 pcm so not even sure if you can to that. I have constant power to them with the key in the on position and when car is running noid light turns on so they're working I even took the rail off and bumped the key and the same amount of gas shot out of all 8 so they all work. I swapped coils around and 5 and 7 still get spark and 1 and 3 still have it. I checked o2 wiring and that's fine I have good grounds and I have continuity back to the pcm for all wires that lead there. So everything is running as it should. Also checked compression and leak down. The last thing I can think of is the tune but i can't imagine how
I switched coils and injectors and still runs like crap. I also checked the wire harness and everything seems fine. As far as I know you can only put the coil on one way where the 4 connect so should br on the right side of the car and as for individual timing I'm not sure what the tuner did its the stock 411 pcm so not even sure if you can to that. I have constant power to them with the key in the on position and when car is running noid light turns on so they're working I even took the rail off and bumped the key and the same amount of gas shot out of all 8 so they all work. I swapped coils around and 5 and 7 still get spark and 1 and 3 still have it. I checked o2 wiring and that's fine I have good grounds and I have continuity back to the pcm for all wires that lead there. So everything is running as it should. Also checked compression and leak down. The last thing I can think of is the tune but i can't imagine how
Something is causing incomplete (thus "rich") combustion or oil is getting in there, like i said. Maybe take one of those cheap harbor frieght scopes and look around in those two cylinders.
Last edited by dreadpirateroberts; Dec 9, 2019 at 02:56 AM.
we looked and did pretty much everything you can think of this is the third set of plugs I put on and 2nd set of wires... We are thinking possibly tune related some how.