Why Is My Car Smoking From The Tailpipe

Many people notice smoke coming from the tailpipe and they ask themselves why is my car smoking? Many people think that the repair is going to cost thousands of dollars, but that is not always the case. So, if you ask yourself why is my car smoking from the tailpipe and how to fix it, read on.

1. Overfilled engine oil

Why Is My Car Smoking From The Tailpipe

A lot of people make the mistake of overfilling their engine with engine oil which results in black smoke coming out of the tailpipe. When this happens people automatically assume that they have a bad engine. If this is the case, do not freak out because this problem is fairly easy to fix.

Adding too little engine oil will definitely cause damage to the engine. But, also putting too much oil in your engine could cause it to smoke. It could also cause severe mechanical damage as well.

When you overfill your engine with engine oil, the oil ends up getting past your oil ring, and your piston rings and reaches the top of the cylinder. From there, it gets into your combustion chamber and then burns off with the air-fuel mixture and then from there, it comes out your tailpipe.

Fixing an overfilled engine is pretty easy. You will have to park your car on a leveled ground. Then check the engine oil level once the engine cools down. Then, drain the extra engine oil.

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Is your engine oil due for a change? Visit our Car Fluid Guide Website to learn the importance of changing your oil on time, which type of engine oil is best for your vehicle, and much more.

2. Bad positive crankcase ventilation valve

Why Is My Car Smoking From The Tailpipe - WHITE SMOKE

You could have white smoke coming from your tailpipe if you have a bad positive crankcase ventilation valve. Basically, your PCV valve or your PCV system is responsible for recirculating the blow-by from your crankcase back into your intake manifold and your engine.

So, when your piston comes up and reaches the top dead center, the spark plug ignites their air-fuel mixture inside the combustion chamber. As the fuel mixture ignites, it expands. As this happens it, pushes the cylinder down in the cylinder bore creating power.

But, some of those gases slip by your piston rings and get into your crankcase. From there, those gases find their way to the cylinder head where the PCV valve under certain driving conditions allows them to be recycled through the intake manifold back into the combustion and be reused.

If you have a bad PCV valve that is stuck in a position where it’s aligned for the maximum flow of the blow-by gases from the crankcase to the engine even when it’s not supposed to, your engine could actually be sucking in a bit of your engine oil and burning it through the tailpipe.

Testing a PCV valve to make sure it’s not the culprit for smoke coming at your tailpipe is fairly easy. You remove it from the valve cover and shake it and make sure that the valve can move around freely.

3. Engine running rich

Why Is My Car Smoking From The Tailpipe - BLACK DARK GRAY SMOKE

If you have black or dark gray smoke coming from your tailpipe, it could be due to your engine running rich. Running rich is when you have too little air but too much fuel entering your combustion chamber. Here are some reasons why your engine is running rich.

  1. Dirty or clogged air filter. The main culprit for why your engine might not be getting enough air into the combustion chamber is going to be a super dirty or clogged air filter. If your air filter is clogged, it’s not going to allow for enough air to go through the air duct and find its way to your combustion chamber.
  2. Faulty fuel injectors. The other reason why you might be having too much fuel entering your combustion chamber could be a little bit more tricky. However, the reason for that is going to be leaking or stuck open fuel injector.
  3. Faulty O2 sensor. The O2 sensor is there to regulate the air-fuel mixture. It tells your car computer whether there’s too much fuel in the exhaust fumes coming at your combustion chamber, or whether it’s too little fuel coming at the combustion chamber. Then the car computer calculates if it should add more fuel. When the O2 sensor is bad and tells the computer that there’s not enough fuel in the combustion chamber, the computer keeps adding fuel and therefore returning their fuel mixture and potentially causing smoke coming at your tailpipe.

4. Engine burning oil

Why Is My Car Smoking From The Tailpipe - GRAY BLUE SMOKE

If you have bluish or grayish smoke coming from your tailpipe, it could mean that your engine is burning oil. This usually happens on engines that have a lot of miles on them, or on engines that have not been maintained properly. This is why I always tell people how regular oil change is important.

What happens when you neglect an engine is your piston rings and your oil ring wear out and they cannot properly clean and scrape down the oil that gets on the cylinder walls. Because o that, the engine oil gets into the combustion chamber and burns together with the air-fuel mixture, and causes bluish or grayish smoke to come out from the tailpipe.

Another reason why your engine could be burning oil is if you have bad valve stem seals. The valve stem seals are rubber parts and are right in the center of the spring. It wraps around the valve. Generally speaking, bad valve stem seals causing smoke at the tailpipe is not very common these days. This was more common with the older made vehicles.

Don’t confuse the smoke from the tailpipe with the condensation smoke that you see early in the morning. When you start your car on a cool morning, that’s just simply the hot exhaust fumes hitting the cold air and condensing and making it look like smoking.

5. Engine burning coolant

Why Is My Car Smoking From The Tailpipe -WHITE SMOKE

If you have white smoke coming at your tailpipe, it could mean that your engine is burning coolant. So, the main culprit when your engine is burning coolant is going to be your cylinder head gasket.

The cylinder head gasket is the gasket that goes between your cylinder block and your cylinder head. That gasket that goes between them is called the head gasket. When that goes bad, it allows for the coolant that’s usually routed around your cylinder bores and your combustion chamber to sneak or leak into the combustion chamber. Then the coolant gets burned off with the air-fuel mixture and causes smoke at your tailpipe.

However, when an engine is badly overheated, the engine block can develop a crack and allow coolant to enter the combustion chamber. The catch is you cannot definitively diagnose this issue and say it’s the head gasket or another crack in the block unless you take the engine apart and test the cylinder head for cracks.

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Hi there. I am a certified Automotive Service Excellence (ASE) mechanic since 2018 and a car detailer for 10 years.

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