1. If your car is difficult to start, need to crank multiple times, vibrating during drive, obvious feel of lack of power, it might be the spark plug is faulty. You may take out the spark plug and check if it is burnt. If the tip appear black mark, broken or melted means the spark plug is spoiled. Suggest to replace at workshop. Take note, the spark plug is a wear and tear item and it designated lifespan is normally around 20k kilometer. Some high end spark plug which made with iridium or platinum may have a lifespan as long as 60k kilometer.
2. If your engine have harsh vibration, producing "klak klak" kind of metal knocking noise, "popping" sound coming out from exhaust, rpm stay low when accelerating, it might be cause by advance or delayed ignition timing. Suggest to diagnose at workshop. Kindly take note, advance ignition will cause backfire, intake system will have knocking. Delayed ignition cause "popping" sound from exhaust.
Suggest to proceed to workshop for repair, usually the keypoints of diagnose are:
1. Check the car ignition system and start up circuit diagram.
2. Check if the spark plug still in good condition, replace if spoiled. Suggest to replace all spark plug at once because using a mixture of old and new spark plugs might cause engine vibration, weak acceleration and higher fuel consumption.
3. Check and tune the electronic ignition system, correct the advance or delayed ignition.
4. Start the car to check and tune all replaced part.