Black smoke, or any other colour smoke for that matter, is not a good sign.
You service your car regularly and follow the manufacturer’s recommended intervals.
The engine oil, oil filter and spark plugs are changed. But now, black smoke is coming from your exhaust pipe/s.
Here are three possible causes.
1. TOO MUCH FUEL IN THE MIXTURE.
With older cars that run on carburettors, it means a tuning of the carburettors is necessary. This isn’t complicated, but it requires some know-how that many young mechanics do not possess.
Some cars with early versions of fuel injection also require adjustments to the air-fuel mixture to eliminate black smoke emissions.
Left unchecked, the condition will cause fouling of the spark plugs and carbon build-up in the combustion chambers.
Most modern cars have electronically controlled fuel injection, which cannot be manually adjusted.
2. THE AIR FILTER HASN’T BEEN CHANGED.
One element that is frequently forgotten during service is the air filter. As a result, many cars continue running with impaired or clogged intake filters.
This can cause the engine to run on a fuel-rich mixture, resulting in black smoke.
3. THE MASS AIR-FLOW SENSOR IS DIRTY.
The mass air-flow sensor is a component in the air intake tract. It measures the quantity of air entering the engine.
Over time, the sensor gets covered with a fine dust that escapes the air filter.
When this happens, the electronic controller receives false air-flow information leading to incorrect fuel management. This can also lead to black smoke.
Cleaning the air-flow sensor is not difficult. There are aerosol sprays you can buy for this. Look for “MAF Sensor Cleaning Fluid”.
A mechanic would usually remove the throttle body that houses the sensor and clean it by spraying over the sensor.
As it is a delicate electrical component, this procedure requires extreme care.
The difference a clean air-flow sensor makes to performance and fuel efficiency can be stark.
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