A) Mostly carbon buildup problems seem to be related to VW and Audi direct-injection cars. There are comparatively few reports for Ford EcoBoost and Cadillac DI cars. Which means it varies considerably by implementation, and the Germans got it wrong for some reason. I'm sure they've fixed by now, but the important thing is that the problem is not one that can't be engineered around.I've been reading alot of negative things about direct injection. I think this is the first car I've owned with direct. I had a 2014 Volt. Just got a 2016 Saturday. Now I'm paranoid about the deposit build up that will happen on the 2016 engine
We had a 2011 Acadia with that engine. We didn't have it long enough to experience any engine problems, but I did notice a fair amount of soot on the exhaust pipe finishers. After one of the oil changes, I sent a sample to Blackstone Labs for analysis. Even though I was using Pennzoil Platinum, Blackstone estimated the oil life at 4000 miles....GM's solution was to tighten up the oil life monitor so that is only goes about 4000-4500 miles between oil changes. This seems to continue today, because our 2017 Acadia still won't go much more than about 4500 miles between oil changes...
That's an old mechanics trick (water to remove crud ), we would block the radiator until the engine temp was almost boiling then spray a water mist into the intake with the throttle wide open until the engine would almost die and the crap would come out of the exhaust in a big blast. Saved a lot of work of dismantling and scraping carbon.I just pulled my manifold on my 2013 Volt to replace the coolant heater, and can confirm it is port injection on Gen 1's.
I used to work on VW's and the TSI 2L turbos were notorious for carbon build-up. We'd upsell a cleaning whenever manifolds got pulled or replaced. They had direct injection, and buildup would almost always happen. How you drove only changed when it would become a problem. I believe it mostly was because of oil getting circulated back in through the crankcase breather.
This is because there's no gasoline to wash the valves off, unlike port injection. No amount of fuel cleaner put into your fuel tank can help either. There are ways to clean them by injecting cleaners into the manifold with the engine running at high idle (results may vary). During the Tax Day floods, we had many waterlogged cars come in. I pulled the manifold on one that had sucked in water, and the valves were clean as a whistle. Engine was saved btw. I do not recommend dumping water into your engine to clean them though.