Backfiring and sooty plug

My truck has been running like crap lately. Under load it coughs and backfires. When this happens the vacuum gauge will jump up 1-2psi. The plugs look fine, besides number 7 which is dark and sooty. I did a compression test on #7 and a few others and it checked out fine. It also sounds like I have a second wastegate on the driver's side(that might just be in my head though).

Changed fuel filter, plugs, swapped coil packs around, checked fuel pressure.

I'm going to drop my crossover and take a look at the flex pipe. Will also move #7 injector and see if the dirty plug follows. I was just wondering if anyone else came across a similar problem.

Exhaust leak? Our turbo truck was doing it. It ended up being leaking manifold on turbo side. But all our plugs were covered in soot.

I'll have to check for leaks. It doesn't sounds like it has an exhaust at idle or during normal driving. But, like I said earlier, the wastegate seems to be sounding a lot louder than before.

When this problem first started, was after driving about two miles after hitting the rev limiter. Figured I'd throw that out there. But I think if hitting the rev limiter screwed something up, it would have showed symptoms immediately, not two miles/five minutes later. I don't know...

What's the plug gap

What about your wideband readings

.026-.028 is the gap. Currently running NGK B8EFS plugs.

Wideband readings are close to normal. Might be running a little leaner than before. I'm always changing fuels and running meth, so my AFR's aren't too consistent.

Hit the injectors with some brake cleaner tonight and it seemed to have fixed the problem. Didn't think it would be that easy, haha.

I have had 3x motors with boost give me a sooty #7 plug, as well as three broken #7 pistons on each motor. This was when using stock truck intake. Switched to TBSS intake, problem solved. Sold the turbo as well as solving the problem. I blame sooty plugs on poor flowing truck intakes.

Stock gmt800 intake has worked well for a lot of members even farm truck used one hell the pioneer of boosted silverado ran one....

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Originally Posted by MrHorsepowerLSx

I have had 3x motors with boost give me a sooty #7 plug, as well as three broken #7 pistons on each motor. This was when using stock truck intake. Switched to TBSS intake, problem solved. Sold the turbo as well as solving the problem. I blame sooty plugs on poor flowing truck intakes.

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What kind of fuel were you running? Were you spraying Meth?

I'm going to stick with the truck intake for now. Going to send the injectors out to be cleaned/flowed and go from there. Also going to try and get back to running at least 50% Ethanol fuel for added safety, along with the water/meth i'm spraying.

Had a mishap with #7 this week myself. Not blaming the truck intake as the root cause but I will not be using it on my 6.0 build . http://i1057.photobucket.com/albums/...psc7820a83.jpg

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Originally Posted by jansen

Had a mishap with #7 this week myself. Not blaming the truck intake as the root cause but I will not be using it on my 6.0 build . http://i1057.photobucket.com/albums/...psc7820a83.jpg

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that isnt intake issue. that is coolant temp issue with too much timing and lean AFR....cylinder temps got hot, egts thru roof

That's why I said I was not blaming the truck intake as the root of the cause.

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Originally Posted by Beatdown Z

What kind of fuel were you running? Were you spraying Meth?

I'm going to stick with the truck intake for now. Going to send the injectors out to be cleaned/flowed and go from there. Also going to try and get back to running at least 50% Ethanol fuel for added safety, along with the water/meth i'm spraying.

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93 Octane, with a sno perf kit. I only have 10% Ethanol here in Jersey. I don't really "blame" the intake, but changing it reaped me better results in my favor changing it out, and i had better luck with the setup after it was changed. Must have been a coincidence lol. I had an EGT gauge in my truck and it would scream until I started spraying it with meth, then the heat levels came down to a much happier level when I was beat the snot out of it.