Direct injection is all the rage right now, but I was surprised to learn that there seems to be some issues with it. A friend of mine has one of the newer turbo BMW 335i’s that use direct injection and he was asking me if there was anything that he could do to clean the deposits off of the intake valves. This was a surprise to me since I have rebuilt port injected engines that had high miles on them, and the valves looked very clean. To show what he was talking about, he sent me this link:
The problem seems to be that since no fuel ever touches the valves like in a port injected engine, the valves never get ‘washed’ and are thus left to grow these deposits. This happens even with very low miles on the engine. This is further compounded on my friends turbo car which has a lot of pressure in the crank case from blow-by, which then pushes oil through the PCV system into the intake. This is why the buildup on the BMW valves in the pictures are so big. The problem is also not unique to BMW: Audi and even Ecotec owners are complaining of a similar situation.
I find it strange that somehow during development and testing of these engines, the engineers were ok with this? They must have run into this problem in the lab!