My Toyota Corolla 2010 started to make a strange rattle sound at cold start. It's a common problem
and on youtube you can find many Toyota Corolla owners describing this problem. Toyota itself
claims that this might be due to a problem with the VVT (variable valve timing) cam-gear and
the fix would be to replace this part. I am not really sure that this true or that there is just a single cause for this start-up rattle.
My theory is that the fault
on my car was due to the chain hitting the case and rattling for a second at startup. In any case I don't know
the exact mechanical cause but I know the symptoms and I know that it was possible to fix this
at a cost of 10$ without visiting a Toyota garage.