LS6427

iTrader: (2)

The bumper is getting black after a few days and when the pedal is hammered a HUGE cloud of black smoke comes out the whole time the pedal is down.

Can JUST the mixture be leaned out easily?

gr8vet

No, do not need a dyno tune to lean engine. Do need a wideband to verify your changes. Did you have any big changes? Sounds like more than a lean mixture, using oil?

LS6427

iTrader: (2)

Yup, using lots of oil. 1 qrt every 300 miles. Does that mean there's too much blow by and the PCM is spraying more fuel?

edcmat-l1

iTrader: (10)

Sounds like you have serious issues.
Theres no way to tell if you need to completely retune it without first seeing the tune. But, it doesnt sound encouraging.
You can tune just the WOT fueling, but thats only gonna fix the black cloud when you're in it hard.

wait4me

iTrader: (10)

I would definatly take it back for a retune if possible. If you paid for a dynotune and it is doing that, the fueling is not correct.... Not sure if they just tuned it wrong or you have a bad part on your car, but if it where me i would not "floor" the car untill it was checked out.

LS6427

iTrader: (2)

It was only tuned once 5 years ago when it was installed. The engine is 5 years old now (50,000+ miles, LPE 427) and has been blowing the black smoke more and more over the past year. Solid black. But as far as the engine goes, its literally running like the day I first started it, perfectly. Great oil pressure at all times (5-psi on start-up and really never drops below 38 unless its scorching hot out with the A/C cranking) and its still a powerhouse, smooth and silent in every way.

So do you think my rings are just shot and I'm getting blow-by?

Also, if the PCM is making it rich solely because of the blow-by, will a re-tune be a waste? If so, I'll just drive the car normally until I can tear it down and rebuilt/replace it. Because when driven normally or not so aggressively, there is absolutely zero black smoke and it runs perfectly.


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