Most car fuel systems these days use direct fuel injection (commonly referred to as DI or GDI). This means that gasoline is injected directly into the combustion chamber instead of through the air intake manifold, as in older vehicles.

The problem this creates is that the gasoline no longer cleans the air intake ports during its trip to the combustion chamber like gasoline injected into the intake manifold does, so the buildup of oil vapors only gets worse over time, causing heavy carbon and sludge deposits. These deposits will usually create problems at around 80–120,000 kilometers (depending on driving habits and fuel used), where cold start misfires will become noticeable, and eventually, if nothing is done to help the problem, the car may lack power in addition to having poor fuel economy and constant misfiring.

At this point, manual cleaning is required. BMW has developed a valve cleaning process using walnut shells. A service that we offer for BMW, Volkswagen, and Audi. Removal of the intake manifold is necessary to clean the intake ports manually using this aforementioned ¨walnut-blast” as well as small cleaning tools, like a trip to the dentist.

The most common engines that are affected by this are the 1.8–2.0 TSI, found in many Volkswagen and Audi products like the Golf (GTI,R, TSI), as well as the Tiguan, A3/S3, A4/A5, and the Q3/Q5’s. BMW and Mini are also heavily affected by this problem.

Preventive service can help though. BG chemical decarbonization cleans intake ports using a special device. This is recommended every 30,000 kilometers, or 2 years, to avoid the need for major cleaning. This has to be performed either after a manual cleaning has been performed or as soon as the vehicle reaches 30,000 kilometers.