If your car check engine indicator light up, jerking when driving slow or during accelerating, engine vibrating, it might be cause by spark plug or ignition coil faulty which lead to engine mis-firing. Sometime it might not be the spark plug issue, it maight be the carbon deposit causing the jerking. Problem can be solved by cleaning the spark plug. 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 owner not to continue driving when the check engine indicator light up, identify the error and proceed to repair at workshop.
Suggest to diagnose at workshop, usual keypoints of diagnose are:
1. Check the car ignition system and start up wiring.
2. Check the condition of the spark plug, replace if it is faulty. It is suggest to replace all the spark plugs at the same time. Mixing new and old spark plugs may cause problem like engine vibrating, weak acceleration, and higher fuel consumption.
3. Check the condition of the ignition coil, replace if necessary.
4. Start the car to perform inspection, tune all replacement parts.