5.3L runs fine but blows heavy black smoke

[Bad Influence]

BACKGROUND - I bought the truck knowing it had issues. It had rough idle and acceleration was terrible. It would spit and sputter and then take off hard after 2500rpms (no black smoke....yet). OBDII scanner said # 6 cylinder misfire so I started blindly throwing parts at it.

INSTALLED PARTS - fuel filter, plugs, wires, #6 injector, #6 coil, seafoam, new front passenger side (upstream) O2 sensor, K&N cone filter (cost me nothing so figured why not)

Since the new parts, the truck accelerates fine but still idles rough 90% of the time. OBDII scanner now says "Bank 2 system too lean" and "random cylinder misfire"... I have also removed the cone filter and put the stock air filter back in.

The truck starts and idles rough but runs fine with plenty of power under acceleration, but it blows heavy black smoke. The even cylinders (passenger side) spark plugs are as black as can be while the odd cylinders (drivers side) are not black in the least.

I know this means the fuel mixture is entirely too rich... my question is have you heard of this before? What would you suggest doing next? I would rather not take it to a dealership for a diagnostic because I will almost be obligated to let them fix it.

Thanks in advance for some helpful input!

 

[Jounier11]

Sounds like who ever used to have this truck always put bad gasoline in it like citgo or some cheap gas nothing like chevron or shell so remember when u put gas put stuff like chevron,shell,mobile, or 76(if available) if not use something like chevron with techron and as for the black smoke if it's really heavy like the 96' tahoe i had (which did the same thing) then i would say it's time to replace those fuel injectors (which will cost u about $300 for just the parts) and about another $300 for installment and having to clean out all the black stuff like carbon dioxide in the place were your fuel injectors go!!!! Depending on what year your Hoe is!!!!

 

[Jounier11]

Or u could go to autozone and get some Lucas Fuel Injector Cleaner But u have to Fill Her up to clean them out not sure if that will clear the black smoke but ill will probably increase fuel mileage!!!

 

[gtrzfan]

I just ran into this exact thing with mine. After changing plugs and wires and cleaning the intake with no change at all, I replaced the upstream drivers o2 sensor. Instantly cured it. I'm going to replace the other 3 o2 sensors shortly to make sure i dont run into this problem again. Going to order them online and save a ton of money on them compared to local stores.