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Hello I'm Mike. The direct injection system on these engines causes build up on the intake valves. It is very common. To fix this. You just need to remove the intake manifold. And clean the intake valves. Just have to scrap the the build up off the valves and around the valve seats using a pick set or if you have a walnut blaster that's the easiest way.
Because of injectors are directly in the combustion chamber there is no way for the fuel to clean the back of the intake valves so it build up with carbon and oil coking. So when the engine is cold started the carbon is hard which causes the valves not to seal which makes the engine misfire when cold started.
This is a major problem for all manufacturers that use direct injection.
When I replace intake manifolds under warranty I usually offer to clean the intake valves since the manifold is already so it saves the customer some money.
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