wrench97

Blow by is excessive crankcase pressure, many years ago before emission controls it would vent out of the road draft tube now a days it usually ends up in the air intake piping/air filter assembly from a hose connected to a valve cover or directly to the crank case in some cases. It can be caused by defective rings, piston, valve guides, or a blown head gasket in rare cases. If you have a MIL(Check Eng Light) illuminated a scan tool will give you a code or codes if the light is there isn't any guessing involved if your mechanic can't give you a better explanation then what you got it's time for a new mechanic.