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HomeFeatured ArticlesCar Exhaust Smoking? Here's Why

Car Exhaust Smoking? Here’s Why

Your car is smoking! And sometimes that’s not a compliment.

What if your car tailpipe is smoking like a chimney? Well, we know the tailpipe is meant to expel gases. However, in most cases, if you spot a trail of smoke following your car, it can mean nothing but trouble. This is because the fumes that come out of the tailpipe might not always be the right kind. Besides, the car manufacturers are moving towards more efficient internal combustion engines by making use of advanced converters. All this means modern cars hardly leave any visible smoke or gases behind.

But there are times when you take a glance at your rearview mirror and you can’t help but notice the dark smoke marking your car’s path. If your car exhaust spits funny, you need to check out this blog post right away.

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Smoke coming out of the hood

To put it simple and straight, smoky tailpipes are a sign that your vehicle isn’t healthy and needs repair. It can be frustrating to realise that you’ve got smoke coming out of your car. You can bet something is wrong if the smoke is leaking out of the hood or the tailpipe. But figuring out the problem isn’t always easy.

How a Car Exhaust System works

The burning of fuel in each cylinder creates exhaust gases. These gases then make their way out of the chamber. They then flow through the exhaust manifold and into the exhaust pipes. In between, these gases travel through a Catalytic Converter where the harmful, poisonous gases are sifted down to the accepted level of emission. This procedure also reduces the gases into water vapour and carbon dioxide. And finally, its exits through the tailpipe.

When everything’s working correctly, this exhaust is colourless. But if something is amiss, you’ll see a cloud of smoke coming out of the back of your car.

There are three common colours of exhaust smoke emitted from a gasoline-powered engine:

  • White
  • Black
  • Blue/Grey or Grey/White

White Smoke

Most white smoke emissions are normal. It is a part of the combustion cycle which happens when we start the engine of the car. Condensation turns into a vapour which can look like white smoke. As the engine warms up, the condensation dissipates and the white exhaust smoke (steam) is no longer seen. If excessive white smoke is observed even after the engine warms up, this could be a signal that there is trouble around the corner.

Car Ignition Barrel
White smoke is natural when you are just starting the car, bringing the engine to life.


  • Coolant Leak: A telltale sign if coolant leak is seeing odourless white smoke along with low coolant levels. Besides, milky looking engine oil is also an indication. This means that the coolant has found its way to the combustion chamber and is being burnt. If your engine is overheating and you find yourself topping up the coolant very often, this might be the case of a coolant leak.

    essential car services
    If you find yourself topping up the coolant very often, this might be the case of a coolant leak. 
  • Bad Fuel Pump Injector– When the fuel injectors go bad, they reduce the amount of fuel delivered to the engine. This also causes white smoke from the pipes. Fuel pump injector failure is a very common occurrence in diesel cars.
  • ECU Error: If the ECU or the Engine Control Unit malfunctions, it could very well tick-off the fuel timings. This in turn would cause inefficient combustion cycle which can also produce a lot of white smoke.

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Black Smoke

Black exhaust smoke means the engine is burning too much fuel. Hence, the exhaust is spitting nothing but carbon.


CNG Car maintenance Tips
Air Filter
  • The first thing you should check is your air-filter and other intake components like sensors, fuel injectors and the fuel pressure regulator.
  • Clogged fuel line: If your car’s fuel lines are clogged, there could be dark smoke coming out of the tailpipe. Black smoke is usually the easiest issue to diagnose and fix. But burning unnecessary fuel will definitely affect your fuel economy. So don’t think of avoiding this.
  • Carbonised Engine: This happens when the engine is clogged and packed-up with carbon. This required a complete engine de-carbonisation.

Blue/Grey or Grey/White Smoke

Anything other than white or black smoke is tough to diagnose. The smoke can mean a lot of things. But if you see blue-grey smokes from your car exhaust, you can be certain that the engine is in distress.


  • Burning Oil: Blue smoke from the tailpipe can mean that the car is burning oil or is suffering from a lousy turbocharger. Take the same precautions as with any other coloured smoke, and check for excessive oil consumption.
  • Transmission Fluid Leak: Grey smoke can also mean that your automatic transmission fluid is getting burned up in the engine. A faulty transmission vacuum modulator would be the culprit in this situation, leading to transmission fluid getting sucked into the engine and getting burned up.
  • Stuck PCV Valve: Grey smoke could mean a stuck PCV valve. The PCV system (Positive Crankcase Ventilation) cuts down on harmful emissions by recycling them back into the combustion chamber. However, when the PCV valve gets stuck, pressure can build and lead to oil leaks. Fortunately, PCV valves aren’t expensive and can be a quick job for a mechanic at a decent workshop.Excessive smoke from the tailpipe 

    If you spot too much smoke from your car, don’t ignore it. It usually is the exhaust system’s call for help. So if you think the car exhaust system is in trouble, don’t hesitate to take the car to a service centre next to you. Download the GoMechanic App now!You might be interested in CNG + Petrol vs Petrol Only | Which Makes More Sense?

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Akshat Ajeya
Akshat Ajeya
Lead, Content & Creatives at GoMechanic | Automobile Scale Model Collector | DIY guy | Consumer of many foods | CVT is not that bad


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