As I wrote about in a recent post "Keeping Carbon Buildup from Occurring: Best ways to keep clean", the introduction of direct injection is becoming more common and may soon become the standard on new passenger vehicles. This has led to an explosion of carbon buildup issues that can cause faults as well as rob both horsepower and fuel economy. To further demonstrate the extent of these issues, today we will talk about a 2007 Audi S8 and the work that went into cleaning it up.
This customer came in with a check engine light on, but no other drivability complaints. A quick check of the fault memory reviled OBD II fault code P2006 - Intake Manifold Runner Control Stuck Closed (Bank 1). Our experience gave us the feeling that we were dealing with a carbon issue, agitated by cold weather operation. We explained to the customer that in order to investigate further, we would need to pull the intake manifold.
We got to work removing and separating the two halves of the manifold. With the manifold off, it was instantly obvious that our suspicions were correct, as heavy carbon caked the valves and runner flaps. Add a bit of moisture and cold weather, and these flaps will undoubtedly throw faults ranging anywhere from P2004 through P2023. We informed the customer that he was going to need extensive cleaning, so we got to work with our secret carbon busting weapon. BMW Fuel System Cleaner
We soaked the valves that were closed with the cleaner and used small brass brushes with the cleaner to scrub the open ones. After sitting overnight, we sucked the excess cleaner out of the valves and used the brush to clean the remaining valves. Valves soaked in the chemical overnight clean up very quickly where the open ones take a bit more elbow grease. We were very careful not to drop anything into the open cylinders other than the chemical and the chunks of carbon that fall. Bits of carbon will fall into the cylinder, so we remove the affected cylinder spark plug and pour a half ounce of cleaner into it directly. After we let it sit for a while, we insert a compressed air blow gun into the intake port and then cover over tightly with shop towels or rags. We made sure our area was well ventilated and and that we had proper breathing and eye protection, as the chemical is quite toxic if inhaled directly. We blew any remnants of the cleaner out, and sprayed off with brake clean to check the cleanliness of the surface. It was up to us on how clean we wanted to get them, as the cleaner will be further activated once exposed to engine heat and carbon will continue to break and burn off. This means not every surface has to be sparkling clean, as the cleaner should have loosened up the rest and will be further cleaned once the car is running. As you can see; however, we got them extremely clean.
With the carbon removed, we reassembled the intake manifold. We then removed the spark plugs, disconnected the ignition coils, covered the spark plug tubes with rags, and cranked the engine over to shoot out the excess carbon and cleaner. This keeps the engine from hydrolocking and removes a lot of the residual carbon that fell into the cylinder. Again, we take the compressed air blow gun and clean the area. Once reassembled we changed the oil to make sure the cleaner that got into the oil is removed. We then push the vehicle outside and start the engine. This part can be shocking for many, as plumes of white billowing smoke will pour from the exhaust. This is the loosened up carbon that is breaking off and being burnt, so no need for alarm. We let it run for 20 minutes to let it stop smoking. Finally, we take it for a hard test drive and let it idle for 20 more minutes.
Right away, the vehicle felt completely different: more power, more response, and a better overall drivability. We love performing work like this, as when we are done there is such a large, noticeable difference. So many times there are systems and components that are replaced that the customer may not notice. Being that the this is the second owner of the car, this customer was rewarded with drivability he never knew was there. If you are looking for answers to why your direct injection car just doesn't have the get up and go it used to, get in contact with us as we may have an solution to your problem.