Just wondering...for some reason when i leave my car on and its parked it leaves a black residue on the concrete where the tail pipe was ....??? is it burning oil or too much fuel in mixture what can it be im new to blazers just bought car to fix up ...dam rust bucket ....engine is 4.3 vortex...any help would be great thx

 

Yeah, sounds like carbon from a too rich fuel/air ratio.

 

cool thx man prob bad mass air flow