Oil in Intake Manifold: Common Causes and How To Fix

The “oil in intake manifold” is the last thing you want to tolerate because it can significantly damage your engine. There are many ways to fix it based on the cause: repair the faulty PCV valve, clean up oil build-up on the passageways, or replace worn-out rings on pistons, valve seals, or failed turbochargers.

Oil in Intake Manifold

We have the details below. Before the end of this guide, you’ll also learn how to tell when there’s oil in the manifold and, most importantly, to prevent the problem from happening in the first place.

How To Fix the Oil in the Intake Manifold Problem?

To fix the oil in the intake manifold problem, examine the PCV valve and do the necessary repairs. The problem could result from faulty turbochargers, piston rings, or valve seals, which need replacement. You can also fix it by cleaning clogged oil passages to remove oil build-up.

An intake manifold plays a critical role in the internal combustion engine. It helps in the distribution of the air-fuel mixture to the engine cylinders. The manifold features a series of tubes, which distribute air evenly to all the cylinders. The air is necessary during the first stroke of the combustion process.


The intake manifold cools down the cylinders and prevents the engine from overheating. That said, there shouldn’t be any oil inside the manifold because oil intake valves (oil control valves) and fuel injectors are the ones that deal with the supply of oil into the engine. If oil enters the manifold, it indicates an issue with the engine.

So, we will take you through the details of “how to fix oil in air intake manifold.” As stated, the solution depends on the cause of the problem. There are many causes of the oil in the intake manifold. The most common causes include a defective positive crankcase ventilation (PCV) valve, faulty turbocharger, blocked oil path, leaky valve seals, worn-out valve seals, and wrong rings for the pistons.

  • Repair the PCV Valve

The role of the PCV valve is to regulate the vacuum inside the intake manifold. In other words, the valve helps divert blowby gasses and reduce their impact on the crankcase. Thus, when it starts to fail, usually after getting clogged with sludge, the valve allows excessive blowby gasses, which causes too much pressure in the system. That pressure forces oil through the system plumbing, eventually into the manifold (you may also see oil in exhaust manifold).

Note that exhaust gas recirculation can also cause oil into the manifold. This emissions control function sends dirty air back via the air intake to be burned again. As a result, a sludgy or oily build-up in the intake over time. Unfortunately, that’s something you can’t control.

And for those wondering “what causes oil in throttle body?”, the inlet tube is linked to the throttle. But the throttle and intake manifold share the same plumbing. That means when the oil forces its way from the intake chamber into the throttle, it will likely enter the manifold.

You can fix this problem by cleaning or replacing the valve. However, starting with the more economical option – clean-up is always advisable. First, disconnect the battery’s negative terminal using a wrench or pliers. Cutting down the power is essential to avoid potential electrical hazards.

Next, locate and remove the PCV valve (you should find it in the valve cover. Please consult your owner’s manual for the exact location). Once it’s out, clean it thoroughly using a degreasing agent and some rugs (remember to collect any oil residue with the help of an oil catch pan). It’s also good to clean the manifold with the degreaser.

After that, reattach the valve and the battery terminal, then do a test drive. If it doesn’t work, you’ll require an inexpensive replacement (costs around $25 in parts and about an hour in labor).

  • Fix Faulty Turbocharger

A failed turbocharger can cause the oil in the manifold problem. When a car’s turbo fails, the obstructed return line or seals can lead to an oil leak. The oil will usually enter the intercooler but may end up in and on the air intake. So, if your vehicle has a turbocharger, it’s likely that it has failed and triggered the “oil on top of intake manifold Chevy 350” situation.

Fixing Faulty Car Turbocharger

The best solution for a defective turbo is to replace it. On average, expect to pay between $700 and $1,200 for the replacement. If you’re lucky, the problem might not require a complete overhaul.

You or someone with expertise with turbos may be able to repair it. However, that depends on what has failed. Feel free to consult an expert if you need help or advice.

  • Replace Faulty Rings on Pistons

The rings provide a seal between the piston and cylinder wall. They help to ensure that pressurized combustion gasses don’t enter the oil sump (oil pan). In addition, the rings regulate oil consumption by stopping oil from getting into the combustion chamber and burning.

Like any other component, the rings experience wear and tear over time. When they eventually fail, the engine will probably experience an oil leak. This leaking oil could find its way into the intake manifold.

You must take the pistons off the cylinders and identify the damaged piston rings. You do that using a compression test. Experts say that a healthy engine should have a compression of over 100 PSI per cylinder. However, a variation of at most 10 percent between the maximum and minimum is allowed.

Generally, the ring replacement is one of the most expensive repairs and is only a DIY task if you’re an expert. The work involved is complicated and best handled by an expert. Charges range from $1,000 to $5,000, depending on your car type. Also, it would help if you used the correct rings (there are two types – moly and cast-iron rings), depending on your engine’s capacity.

  • Replace Damaged Valve Seals

The valve seals are critical in maintaining an engine’s compression levels. They secure the valves in the cylinder heads and control the oil amount entering the valve stem system. If these seals leak, oil can easily find its way into the manifold through the leaking valves. The solution is replacing all the worn-out seals with new ones.

Replacing Damaged Car Valve Seals

To replace the seals, you may need to remove the cylinder heads. Once they are out, inspect the seals for wear and remove the damaged ones. Experts recommend replacing all the seals because if one has failed, the rest will follow soon.
You can have a professional repair if you need help. The cost usually ranges from $180 to $1,500, depending on the extent of the work.

  • Clean the Oil Passageways

There are oil passageways within the engine through which fluid must flow freely. Oil will probably enter the manifold if these passages are blocked in certain spots. Blocked oil flow ways usually occur due to a lack of oil change.

Suppose the engine oil goes too long without changing. In that case, it will collect sludge and other contaminants and deposit them in the passageways. And when the oil can’t pass through freely, it will go via the PCV valve, and you’ll eventually encounter oil leaking from intake manifold.

To fix this problem, use an engine flush formula. You should pour it into the oil, then run the engine for about 15 minutes. The formula will help clear the build-up within the passageways. After that, change the engine oil and replace the air filter.

Alternatively, you can drain all the oil from the engine and then use wire brushes to remove the dirt from the passageways. However, the method is usually cumbersome and risky. A slight mistake can lead to significant engine damage and costly repairs. Please get in touch with a professional if you’re unsure of anything.

How To Keep Oil From Getting into the Intake Manifold?

To keep oil from getting into the intake manifold, always use the correct oil type and change it regularly. Also, buy and install a top-quality air filter to catch contaminants before they get a chance to clog the engine.

If there’s oil in the intake manifold, fix the problem immediately. The best way to keep oil from getting into the intake manifold is to ensure that you have a properly working PCV system. To do that, you’ll have to follow the practices mentioned above. Let’s discuss them in detail:

  • Use the Correct Oil Type and Change It Regularly

You shouldn’t use just any engine oil on your vehicle. Follow the car’s manufacturer’s recommendations on the correct oil type and always go for the high-quality. Many people prefer 100 percent synthetic oil because it lasts long.

Using Correct Car Oil Type

In addition, you must change the oil regularly or when necessary (obey your vehicle’s oil life monitoring system). Typically, you’ll require an oil change after 3,000-7,500 miles since the last change. A timely oil change ensures that you flush out any oil debris and contamination before they can clog the engine.

  • Buy and Install a Top-Notch Air Filter

Using top-notch air filters is one of the sure ways to prevent oil from entering the intake manifold. Good-quality filters will catch dirt and debris effectively so they don’t block the engine. Ensure you always follow your vehicle’s manufacturer’s recommendations on air filter replacement.

  • Fix the “Oil in Intake Manifold” Issue As Soon As Possible

Stay alert and always keep track of your engine’s performance. If you suspect oil in the manifold, try to fix it immediately or seek the help of a qualified mechanic before the problem develops into a costly repair. Check out our next section to know which symptoms you should watch so you can diagnose the issue on time.

How To Know When There’s Oil in the Intake Manifold?

To know when there’s oil in the intake manifold, consider the tell-tale symptoms, including excess white smoke through the exhaust manifold. You may also notice reduced engine power as the oil often restricts airflow in the manifold. Engine misfires and ruined fuel economy are other common characteristics of this problem.

  • Excess White Smoke

As mentioned, there should be no oil in the air inlet manifold. Even little oil can restrict airflow and trigger many problems, including hard acceleration and rough idling. But the situation may be entirely different when there’s lots of oil in the intake manifold.

The oil can get into the combustion chamber and interfere with the smooth burning of the air-fuel mixture. As a result, your vehicle will produce an emission of excess white smoke through the exhaust manifold.

  • Engine Reduces Power

Another tell-tale sign of oil in the manifold is reduced power for your engine. Reduced power could result from many different factors, including low compression (low oil pressure), worn-out rings on pistons, and a clogged air filter. However, sometimes oil in the manifold can also trigger it.

So, if you suspect having oil in there, you must have the vehicle checked by a reliable mechanic immediately. As stated, if you don’t take action as soon as possible, the oil in the manifold will lead to severe engine damage.

  • Engine Misfires

“Can oil in intake manifold cause misfires?” has crossed many people’s minds, and the answer is a resounding yes! As mentioned, when oil enters the manifold, it disrupts airflow. That means the combustion chamber doesn’t get enough air. Insufficient air in this part of the engine usually results in incomplete combustion.

And when that happens, your engine will misfire. However, it’s essential to note that engine misfires could result from many different issues. These include dirty spark plugs and other malfunctioning ignition components. Thus, proper diagnosis is critical whenever you notice this symptom.

  • Ruined Fuel Economy

We’ve mentioned that when oil enters the air inlet manifold, it interferes with the smooth flow of air into the engine. That renders the engine less efficient. Moreover, oil deposits can form in the combustion chamber, which results in incomplete combustion and ruined fuel efficiency.

Ruined Fuel Economy

Oil in the manifold can also coat the spark plugs, which makes them less efficient at igniting the air/fuel mixture. As a result, the engine experiences reduced power and consumes more fuel.

Some of these symptoms could result from a faulty air inlet manifold. You could be dealing with a case of a bad intake manifold gasket, or the manifold itself has cracked, or there’s a leak somewhere. For that, it’s essential to seek the help of a mechanic for an accurate diagnosis and fixing.

Will an Oil in Intake Manifold Issue Affect the Car Door Closing Tightly?

If you’re facing an oil in intake manifold issue, it is unlikely to directly affect the car door closing tightly. The intake manifold is responsible for distributing air and fuel to the engine cylinders, whereas adjusting car door closing tightly relates to door mechanisms. The two issues are distinct and not interconnected.

What Are the Common Causes of Oil in the Intake Manifold?

Oil in the intake manifold is a common issue with a few causes. One of the main culprits is a faulty PCV valve, which can cause excess pressure in the crankcase, leading to oil being pushed into the intake. Another cause could be worn piston rings, allowing oil to leak into the combustion chamber. Regular maintenance and replacing faulty components can help save gears from too much transmission fluid.


The above was our guide on how to fix the oil in the intake manifold problem.

Here’s what you’ve learned:

  • Common causes of the problem include faulty PCV valves, worn-out piston rings, and valve seals.
  • The solution depends on the grounds which call for a proper diagnosis.
  • Notorious symptoms of oil in the manifold include increased fuel consumption, engine misfires, and excess white smoke.
  • You can prevent the problem by following your car’s manufacturer’s instructions regarding engine oil, air filter replacement, and fixing the “oil in intake manifold” issue immediately.

Now you have the information you need to fix your car. So, do it, and don’t hesitate to contact an experienced mechanic if you need help.

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