AOA. I have a Toyota Premio 2005. The car is running on dual fuel (Gasoline as well as CNG). While converting the vehicle to petrol, the engine starts knocking too much. I tried manual clean up of the whole intake system as well as used injector cleaner so that in case there is any carbon or scaling inside injectors, that can be cleaned. I have also replaced spark plugs. As per my knowledge the efi and vtec engines dont knock. Also as the engine gets older, its conpression ratio decreases which prevents it from knocking. The other thing people suggest is the use of hi octane, but that is not a solution. There must be some mechanical problem behind it.
I would appreciate if anyone can help me to figure out the cause of pinging or pre-ignition.