Smoking from my car-What does it mean

Smoking from my car-What does it mean? Smoking means that the engine is not operating normally.

If you see smoke coming from your tailpipe, pay attention to the color of the smoke; you can use it to troubleshoot engine problems.

Black Smoking
Black Smoking

Black Smoking

Check the adjustment and operation of the automatic choke if the engine is an older one with a carburetor. Check fuel pressure if the engine is a newer one with fuel injection. Also inspect the air filter, and check the OBD system for any sensor fault codes. The OBD system should detect a rich fuel condition, set a fault code (such as P0172 or P0175) and turn on the Check Engine light.


Black smoke coming out of the tailpipe on a vehicle with a gasoline engine is a sign of a rich fuel mixture (too much fuel, not enough air). A brief puff of black smoke may be visible during hard acceleration when the fuel mixture goes momentarily rich.

Under normal driving conditions and idling the exhaust should be transparent. If black smoke is visible all the time and the inside of the tailpipe is coated with heavy black carbon deposits, it would tell you that the engine has a rich fuel condition.

On an older vehicle with a carburetor, a rich fuel condition and black smoke can be caused by,

  • Stuck or misadjusted automatic choke.
  • Leaky metal or hollow plastic float inside the carburetor fuel bowl.
  • This could include a fuel saturated foam plastic float, or an incorrectly adjusted float (set too low).
  • A restricted fuel filter may also contribute to a rich fuel mixture.

On a newer vehicle with fuel injection, black exhaust smoke can be caused by,

  • One or more leaky fuel injectors.
  • Too much fuel pressure (sticking fuel pressure regulator).
  • A faulty MAF sensor or Oxygen sensor.
  • A engine computer fault.

On diesel engines, black smoke in the exhaust can occur during hard acceleration. But if the engine continues to produce black smoke, the engine is getting too much fuel. The underlying cause may be incorrect injector timing or an injection control problem.

Since there is not enough air available to burn all of the fuel, some comes out as carbon particles, which are naturally black. Black smoking is usually accompanied by a strong fuel smell. The engine will run poorly in this state, with reduced power and very poor economy.

White Smoking
White Smoking

White Smoking

The exhaust will have a slightly sweet smell if the exhaust contains coolant. It could also have a burned oil smell if it contains transmission fluid. Check the coolant level and the transmission fluid level. If the coolant is low and/or the engine has been overheating, pressure test the cooling system to see if it holds pressure. If it does not, the head gasket is probably leaking and needs to be replaced.

When only the transmission fluid level is low, add the required type of transmission fluid to bring it back up to the full mark. Inspect the vacuum hose from the transmission for fluid inside. If it is passing fluid, replace the vacuum modulator valve on the transmission.

The causes of white exhaust smoke can vary; however, it is common to see white exhaust smoke when first starting a car, especially on cooler days. This is generally steam caused by condensation. As the engine warms up and the condensation dissipates the white exhaust smoke (steam) is no longer seen.

If excessive white exhaust smoke is present well after the engine warms up, it is necessary to have the car inspected for possible internal coolant leaks. Indicators of an internal coolant leak include billowing white exhaust smoke accompanied by a sweet odor or a low coolant reservoir level. An internal coolant leak can also contaminate the engine oil giving it a frothy, milky appearance. Even small amounts of coolant entering the combustion chamber will produce white exhaust smoke.

One of the main causes of white exhaust smoke and coolant loss is,

  • A cracked or warped cylinder head.
  • Cracked engine block.
  • Head gasket failure caused by overheating.

A cracked head may allow coolant to leak into one or more cylinders or into the combustion chamber of the engine. Dirty coolant, a poorly maintained cooling system, a low coolant level, or a non-functioning cooling fan can cause engine overheating. In addition, engine wear can eventually cause the gaskets to lose their capacity to seal properly allowing internal coolant loss. Intake manifold gasket and head gasket failures are two of the most common sources of internal coolant loss.

Never remove the radiator cap or coolant reservoir cap while the engine is hot or running as it can cause serious injury; always allow the car to cool down completely first. Checking for a low coolant level in the reservoir is the first step in determining if coolant loss is causing the white exhaust smoke. If the coolant reservoir is at the proper level but excessive white exhaust smoke is present, a cooling system pressure check is required to determine where, if any, coolant leaks are located.

Blue Smoking
Blue Smoking

Blue Smoking

Bad news because it means the engine is burning oil. Usually smells like burned toast. Check the oil level on the dipstick to see if the engine is using oil and the oil level is low (add oil as needed to bring it back up to the full mark. DO NOT let the engine oil level get too low or serious engine damage will result ! You can also do a compression check or leak down test to diagnose worn pistons or rings.

The underlying cause is usually,

  • Worn valve guide seals or guides.
  • Broken or worn piston rings.
  • Worn or damaged cylinders.

Oil burning can eventually contaminate the catalytic converter and oxygen sensor. It also increases the risk of the engine running low on oil and losing oil pressure.

Accompanied by an acrid smell, may indicate that lubricating oil is getting into the combustion chamber. Although it is a hydrocarbon, like other fossil fuels, it does not burn well inside an engine and much of the oil comes out of the tailpipe in partially burned or unburned form.

The oil also carries contaminants from inside the engine which undergo changes in the combustion process and contribute to the creation of smoking and unpleasant smells. Really smoky vehicles may use as much as 1 litre of oil every 200 km. Normal engines, however, burn little or no oil in 5000 km of driving.

If you see different colored exhaust fumes it’s time to pay attention to your car. Even if your vehicle isn’t flashing any warning lights, the smoke coming from your exhaust is a signal that something might not be working properly.


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