If your car exhaust producing black smoke after started, it might be spark plug is faulty causing the air mixtures in engine become too rich which lead to uncomplete combustion. Suggest to diagnose at workshop, owner can check the spark plug first to confirm if it is faulty:
1. If the spark plug is burnt, scarring, broken, black mark appear on top, or electrode melted, it tells the spark plug is already faulty and needed a replacement immediately.
2. If the spark plug shown smoked black colour, it tells the spark plug used with incorrect heat range or there is engine oil leakage.
3. If there is deposit between the top and electrode, it tells the engine oil leakage if the deposit is oily, nothing wrong with the spark plug. However, if the deposit is black in colour, it tells there are carbon deposit build up on the spark plugs causing it being by-passed. If the deposit is grey colour then it tells the additive in the fuel covering the electrode causing mis-fire.
4. If the spark plug shown brown red or rusty colour, it means the spark plug is working normally.
5. If the spark plug is greasy, meaning the spark plug electrode gap is out of spec or the fuel is too rich, it might also be the high voltage cable open circuit or short circuit.
Suggest to visit workshop for diagnose, usual key point of diagnose as below:
1.Check the car ignition system and starting circuit.
2. Check if the spark plug still in good condition, replace if it is faulty. Meanwhile it is recommended to replace all spark plug at once. Mixing new and old spark plug might cause car vibrating, weak acceleration and increase fuel consumption.
3. Check the car fuel supplying hose.
4. Start the car and tune all the replacement part to ensure the problem is resovled.