* Valve Cover Gasket Leak: This is the most common culprit. A leaking valve cover gasket allows engine oil to seep into the valve train and eventually find its way into the intake manifold and then the throttle body. The crankcase ventilation system (PCV) plays a role here; if it's clogged or malfunctioning, it can increase pressure in the crankcase, forcing more oil out through leaks.
* PCV Valve Failure: A faulty Positive Crankcase Ventilation (PCV) valve can also lead to excessive crankcase pressure, pushing oil past seals and gaskets. A clogged or malfunctioning PCV system will lead to oil buildup in various places, including the throttle body.
* Breather Hose Leak or Blockage: Similar to the PCV, problems with the breather hose can cause crankcase pressure to build up and force oil out.
* Worn Piston Rings: Severe piston ring wear can allow oil to be burned in the combustion chamber. Some of this oil can be unburned and collect in the intake manifold and eventually the throttle body. This often manifests as blue smoke from the exhaust as well.
* Oil Separator Failure (if equipped): Some engines have an oil separator to catch oil vapor before it reaches the intake. Failure of this component can result in oil entering the intake system.
* Improperly Installed or Damaged Components: During engine maintenance or repairs, components might have been installed incorrectly, leading to oil leaks.
It's crucial to have a mechanic diagnose the underlying cause. Driving with oil in the throttle body can lead to engine damage, misfires, and poor performance. The sooner it's addressed, the better. Simply cleaning the throttle body will only be a temporary fix and won't solve the root problem.
