What Causes a Large Amount of Engine Oil in the Throttle Body?
2 Answers
The reasons for a large amount of engine oil in the throttle body are: 1. Damaged exhaust gas recirculation (EGR) valve; 2. Turbocharger burning oil; 3. Excessive blow-by gases under engine compression, causing oil to flow from the breather tube, EGR valve, or check valve into the throttle body or intake pipe; 4. Loose or detached rocker arm shaft screws leading to excessive oil accumulation in the throttle body. Precautions for throttle body maintenance: 1. Regularly clean the throttle body—excessive carbon buildup can reduce engine power and increase fuel consumption; 2. Apply oil to the fixed metal retaining ring before disassembly to prevent thread stripping; 3. If the throttle opening remains the same after cleaning, excessive air intake may occur, causing engine shaking and poor acceleration during startup.
I've been driving for over twenty years and have seen oil in the throttle body several times. Most of the time, it's due to a problem with the positive crankcase ventilation (PCV) system, such as a clogged or faulty PCV valve, which allows oil vapor to enter the intake manifold and then flow into the throttle body. Internal engine wear is also quite common; for instance, severe wear of piston rings or cylinder liners can cause oil to seep from the combustion chamber and accumulate there. Another possibility is a failed turbocharger oil seal, especially if your car is turbocharged. If such issues are not addressed promptly, the throttle body can become clogged with oil sludge, affecting the air intake and air-fuel mixture ratio, leading to increased fuel consumption, reduced power, and even sensor damage. I recommend not delaying and taking your car to a professional repair shop for diagnosis as soon as possible to avoid turning a minor issue into a costly major repair.
