1. If the engine is making " tu tu" or "pong pong" noise, at the same time the car exhaust is vibrating, it could be due to carbon deposit clogged the fuel injector causing it unable to produce accurate fine mist which lead to engine mis-firing, suggest to check the fuel injector at workshop.
2. If the engine is making "bi bi" noise and come with symptoms like weak starting power or harsh vibration, it might be cause by faulty spark plug causing the engine mis-firing. You may determine if the spark plug is faulty with the below explanation: If the spark plug show serious burnt sign, black mark, broken or melted, it tells that the spark plug need a replacement. Suggest to replace at workshop soonest possible.
3. If the engine is making different noise under different speed such as dull or crips noise, it tells that the internal mechanism of the engine is malfunction causing mis-firing, suggest owner to perform diagnose at the workshop.
Suggest to perform diagnose at work shop, usually the keypoints of diagnose are:
1. Check or replace spark plug, 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.
2. Check or repair fuel injector. Normally fuel injectors are not require to replace all at the same time, but mixing new and old injector may cause each cylinder have different power output which lead to engine vibrating and power loss, hence it is suggest to replace all at the same time.
3. Check the internal mechanism, wear and tear, maintenance and lubricant condition of the engine.