Audi A4 B7 De-Carb: The Downside of Direct Injection
Before I bought this car I had never thought about there being a negative to direct injection. As it turns out, not spraying gas directly onto or in the vicinity of the intakes valves is a bad thing. Without this manifold/port injection, there is nothing cleaning the oil fumes from the turbo and the crankcase ventilation valve. These misty oily fumes deposit on the hot intake valves and are slowly transformed into carbon deposits (see top picture).
The current methods for cleaning this are walnut shell blasting and good old-fashioned scrubbing (the method I used). For this, I bought the brush set in the picture from O'Reilly auto parts and some brake cleaner (B12-chemtool works also).
Start by making sure the valves in the cylinder you are working on are closed (you may have to rotate the engine with a ratchet and socket on the front crank pulley).
Plug the others with an old rag to keep debris out.
Knock off as much as you can with a small pick set.
Fill the cavity with cleaner and scrub. (you may attach a brush to your drill to speed things up)
Suck out the nasty cleaner and repeat until clean.
It takes an afternoon to do the job, but it is pretty fulfilling to do it yourself. I had just bought the car when I did this service. It had ~78,000 miles on it, and I assume this is the first time it has had the carbon cleaned. I plan to use intake cleaner periodically in the next 70,000 miles and I am hoping that it will make the next cleaning go easier.
