Originally Posted by NaturallySmashed
Hello I just purchased a 96 2.3 ranger with 140k on it.. it has oil in the air intake.. it looks and smells like engine oil so i'm assuming that's exactly what it is. From what the guy was telling me it was sitting.. so I'm guessing a valve was sticky and oil shot up through the valve cover vent.. but I really have no idea. Does anybody have a clue?
During high vacuum situations like idle and steady lower speeds, the flow through the PCV system is from the air intake, through the closure tube, through the crankcase, then into the intake manifold and on to the cylinders for burning.
At low vacuum and high cylinder pressure (WOT acceleration, for example), the increased crankcase pressure also forces part of the PCV flow backwards through the closure tube into the air intake. How much flow goes in that direction is related to blowby and that is caused by leakage past the piston rings.
Finding a small amount of oil and/or tarlike deposits in the air intake is normal. If there is an excessive accumulation, then it is probably caused by one of 2 things:
- A severe oil overfill in the crankcase (possible);
- Blowby due to worn piston rings (likely).