Rough or unstable idle
Check engine light on
Increased oil consumption
Oil leaks or pushed-out seals
Excessive oil in the air intake or throttle body
Whistling, hissing, or rattling from the PCV valve area
Sludge buildup in the engine
Poor acceleration or reduced performance
Strong fuel smell in the oil
Blue smoke from the exhaust
Vacuum leak symptoms
Engine stalls at idle
Hard starting
PCV valve stuck open or stuck closed
Hose connected to the PCV valve is cracked, clogged, or oily
Excessive crankcase pressure when the oil cap is removed
Little or no vacuum at the PCV valve hose when the engine is running