QUOTE(davidke20 @ Dec 15 2012, 07:56 PM)
Mengsuan,
The reason for an engine shake involves below parts & concerns, it may be a single element that result the vibration, it could also be a combination fault that causes it. So, here we go:
1) Ignition timing too low
1a) faulty sparkplug
1b) faulty plug wire
1c) faulty ping detector
1d) faulty ignition coil
1e) idling speed too low
1f) vacuum leak
1g) throttlebody not close tight at idling
2) Rich idling
3) Faulty engine mountings
4) Intake & exaust camshaft timing inconsistent. Especially we Campor engine uses twin cam, if go hai cam means mahaicam, vibration & unsettle idling is in-eminent.
5) Exhaust pipe sumbat, backflow result in preignition causes engine vibration
6) Crankshaft bengkok
7) Loose piston ring
8) Flywheel bengkok
9) Wrong petrol (when presence octane insufficient to guard the combustian range, preignition happened resulted in ping/vibration)
10) Last but not least... Its an NGV car.
I'm not saying NGV car must vibrate, but the car was designed for petrol, changing it to drink any other thing than petrol need someone who mastered the whole technology, in order to achive optimal setup. Let's take a wild guess, u have tested other Persoga WITHOUT NGV, and their car generally vibrate less than yours? Let's assume NGV need higher RPM to achive lower torque compare to petrol, if this is he reason, now I understand why full time NGV taxi generally got higher idling speed but very little vibration.
I'm no NGV expert(not even dare to call myself a novice), so I am guessing it has to do with your NGV tuning(if not caused by all those physical faulty parts). Its better if you bring this list and reconfirm with your magician. Hope this help.
Hey david, thanks for your insight. I will look into the spark plugs as the first step of troubleshooting. I haven't changed it in 15000KM already.
When I compared with their Persona, I also made my car run in Petrol mode. Idling speed is the same for both NGV and petrol, shouldn't have any low idling speed issue, neither that preignition will happen because NGV is RON130 and I tested for preignition before.
Other possible reason is:
2) Rich idling (maybe because of screwed up AFR due to undesignated fuel being used)
5) Exhaust pipe sumbat, backflow result in preignition causes engine vibration
6) Crankshaft bengkok
7) Loose piston ring
8) Flywheel bengkok