What Causes Oil in the Intake Port?
2 Answers
Reasons for oil in the intake port are as follows: Normal conditions: Oil in the intake manifold is mostly due to the condensation of engine oil vapor when it encounters cold temperatures. A small amount is considered normal. Excessive oil: If there is too much oil, it is likely caused by a malfunctioning oil-gas separator. Other reasons: Prolonged engine idling; dirty air filter; clogged or deformed crankcase ventilation system; clogged, leaking, or deformed turbocharger oil return pipe; coking of lubricating oil in the turbocharger middle housing; cylinder wear causing piston ring gas turbulence; excessive flow resistance in the exhaust system.
When working part-time at the auto repair stall, I often encounter oil in the intake port, which is mostly caused by a clogged PCV valve or damaged turbocharger seals. Oil vapor leaks from these areas and accumulates in the intake manifold, leading to severe carbon buildup over time, affecting engine operation and even damaging spark plugs. If you notice difficulty starting the car or a sudden increase in fuel consumption, these components should be checked immediately. I've seen many car owners neglect this issue, resulting in costly engine overhauls. It's advisable to regularly clean the PCV valve or replace the sealing rings as a preventive measure—it's low-cost and can extend the vehicle's lifespan.
