5 Causes, Signs and Fixing of Oil in Throttle Body

Imagine that you’re driving down an open road, enjoying the smooth hum of your engine, when suddenly, your car’s performance drops and vibrates strangely. You think something might be wrong with your vehicle, and when you look closer, you find oil in car throttle body.

This seemingly insignificant issue can have far-reaching consequences on your engine’s efficiency and overall health.

What exactly is the oil in throttle body problems, and what aspects of this problem will we explore? What are its underlying causes, warning signs, and practical solutions? Why must every vehicle owner understand how to address this issue, ensuring peak engine performance and a trouble-free journey ahead?

oil in the throttle body

What Causes Oil in Throttle Body?

You might ask yourself, “why is there oil in my throttle body?” It is, however, essential to know that oil in the throttle body can result from various factors, like clogged pcv valve, excessive engine oil, damaged seals, faulty piston rings or old vehicle engine. Each reason requires specific attention to prevent further damage. Some common causes include:

1. Positive Crankcase Ventilation (PCV) valve

The PCV valve is prone to getting clogged; excess pressure builds up in the system when clogged. The pressure will then force the oil to flow through another direction, causing oil in intake manifold, then flowing to the throttle body.

The throttle body shares the same inlet tube as the intake manifold, which makes it easy to escape from the clogged PVC valve to the throttle body.

Once the oil escaping to the throttle body is excessive, you will notice smoke from the exhaust will be evident.  

2. Overfilling Engine Oil

Overfilling the engine oil could also build up excessive pressure in the engine. In this case, the oil will try to escape from the wrong place. The excess engine will reach the crankcase, which will then be forced to the throttle body.

In some cases, the excessive pressure caused by too much oil can push oil through the breather and onto the throttle body. Signs like idling issues and reduced power will be evident.

3. Faulty Gaskets or O-rings

Space is created once the gasket or o ring is damaged, allowing oil to slip through. The leaking oil will eventually slip through spaces in the engine before getting to the throttle body.

The gasket or O-ring can get damaged due to wear and tear, high temperature, oil pressure, etc.

4. Use of Wrong Piston Rings

When selecting piston rings for your engine’s combustion chamber, it’s essential to consider their type – cast iron or moly rings. The choice depends on your engine’s capacity.

Using piston rings that cannot handle the blow-by gasses generated by your engine can lead to excessive pressure on the crankcase. Consequently, the crankcase will push oil into the throttle body.

5. Aging Vehicle

As cars get older, their performance and fuel economy naturally go down. One reason for this drop is that engine seals and rings weaken over time, especially in engines with many miles.

Blow-by gasses can’t be stopped because these parts aren’t as vital as they used to be. It lets too much gas out, which pushes oil out of the system. Because of this, oil starts to build up in the intake pipe and throttle body.

Symptoms of Oil in the Throttle Body

Oil on throttle body has many signs that can be easily noticed. The most obvious ones include the loss of power and rough idling. You will also see the check engine light will come up.

Below are oil in my throttle body symptoms.

1. Rough Idle

If the throttle body is oily, it can stop the engine from getting enough air, leading to poor combustion and a rough idle. If the throttle body is dirty and causing rough running, you may notice a low idle when you start the car, pauses when you stop, jerking movements, and strange noises.

2. Fuel Consumption

Using a lot of gas could be because the throttle body is dirty or oily. If the throttle body is dirty, it may not let in enough air, which will cause a reduction in the power generated by the engine. As a result, the car computer system will be notified by sensors.

In addition, to compensate for lost power, the computer system may call for more fuel to enter the engine system. As a result, the vehicle will consume more fuel to create the needed power to work.

3. Check the Engine Light

Excessive oil in the throttle body can trigger the vehicle’s onboard diagnostic system, illuminating the check engine light on the dashboard. Airflow could be restricted as long as oil is on the throttle body. It will affect the working condition of the engine and then trigger the check engine light.

4. Reduction in Engine Efficiency

Throttle bodies in modern vehicles are crucial as they use sensors to measure incoming air. This information is sent to the engine’s computer, which adjusts fuel injectors in each cylinder to maintain the correct air-fuel ratio.

However, oil on throttle body disrupts this process, resulting in an improper air-fuel mix and reduced engine power, making acceleration difficult.

Once you continue to experience these symptoms, if the cause of the problem is not fixed it could lead to a throttle body failure.

How to Fix Oil in car Throttle Body

Getting rid of oil in the throttle body requires an approach that focuses on the problem’s source. Here are the steps to take to solve this problem:

Inspect the PCV System

Check to see if the PCV valve and lines are broken or clogged. Replace any broken parts and remove any dirt or dust that might stop the system from working correctly.

Replace Valve Seals

If old valve seals are found to be the problem, they must be replaced right away. This fix might require taking apart the top part of the engine, so it’s best to let a professional do it.

Address Engine Oil Level:

If the problem was caused by putting too much oil in the engine, drain the extra oil to the amount recommended in the manufacturer’s manual. Change engine oil as recommended following accurate process.

Check and Replace Gaskets or O-rings

Inspect the throttle body gaskets or O-rings for any signs of leakage or damage. Replace them if necessary to ensure a proper seal.

Can a Dirty Throttle Body Cause Misfire?

Yes, an engine failure or misfire can be caused by a dirty throttle body. Over time, dirt, carbon deposits, and oil can build up inside the throttle body, making it harder for air to flow through. This blockage can throw off the ratio of air to fuel, which can cause partial combustion and engine misfires. Regular maintenance, like cleaning the throttle body, can stop this problem and make the engine run more smoothly.


Oil in throttle body can have a significant effect on how well a car runs and how much gas it uses. To find the problem and fix it quickly, you need to know what caused it and its signs.

Regular maintenance and checks of the PCV system, valve seals, gaskets, and throttle body can keep the engine going smoothly and stop oil from building up. Keeping the throttle body clean can also help keep the engine running smoothly and stop misfires. By getting rid of oil buildup in the throttle body as soon as possible, car owners can ensure their engine works well and extend the life of their car.

Akindayini Temiloluwa

I am Akindayini Temiloluwa, an automotive expert writer and car enthusiast. I have over three years of experience in the automotive writing niche and have completed over 300 pieces of content from 50 projects. I have vast knowledge and skill in vehicle repairing, all mechanical work, car upgrades and maintenance. My goal as an automotive content writer is to simplify the most challenging concepts for my readers, help them self-diagnose what may be wrong with their vehicles and offer real value for their time.

Recent Posts