I have a Perodua Viva Elite (2011 MT). Several months back my vehicle engine started to knock and Engine Check Light started showing up while driving in traffic. So I went for an Injector replacement, then every thing was back to normal. But now it seems that the problem isn't solved at all. Now it's been about 8 moths after the injector replacement and guess what the knock is back again.
So I would like to know, what causes the engine to knock?