Porsche 997: Why Your Car is Experiencing Carbon Build-Up

This article applies to the Porsche 997 (2005-2012).

Porsche prides itself in always evolving and improving, and most would say that's the reason why their many racing programs span multiple types of racing across the globe. Everything from Rally cars to 200+ MPH endurance race cars work overtime to develop engines and other systems that later make it to the showroom floor for us to acquire. There is a downside of always evolving – the possibility for problems – and even though Porsches go through rigorous testing, nothing compares to true time and mileage.

Halfway into the production cycle, Porsche models 997.2 were upgraded to a new type of fuel injection system called "DFI," which stands for Direct Fuel Injection. This system differs by directly injecting the fuel into the top of the cylinder instead of the intake manifold. While delivering smoother power band and acceleration, it has risen concerns of reliability and issues with carbon build-up. Below are the most common reasons for the presence of carbon build-up in your Porsche 997.

Potential Causes of Carbon Build-Up

Air Oil Separator (AOS)

The engine's air and oil separator is located on the right corner of the engine. It performs the basic function of collecting the residual gases and vapors that exit the crankcase and funneling them back into the combustion chamber for them to be ignited properly. Sounds fancy, but it mainly acts as a vacuum and blower. Often the AOS can be defective and not process the gases as it should, therefore delivering an unhealthy amount or imbalance of un-ignited gases to the chamber. Over time this will build up and create gunk, which can be noticed in the form or large amounts of white smoke.

High RPMs

While this one is the most elusive one of the believed reasons for carbon build-up, there are knowledgeable forum members that claim that high temperatures of constantly driving your Porsche hard, and on the high-level RPM range, could cause carbon build-up. The logic behind this is that the new DFI system cannot inject as much fuel as quickly into the cylinder; while that makes sense, many may argue that Porsches are meant to be driven hard, and, therefore, it's less likely.

Cheap Gas

This has been a common problem in other DFI engines such as in BMW and Mini Cooper. DFI systems are very delicate and, when developed and tested, are engineered to work with a particular range of octane and quality of fuel. And if any user or owner were to step outside of that range, they run the risk of the DFI system improperly processing the gas. Think of dirty water trying to flow through a filter; obviously, it wont go through very easily. Then imagine clean water trying to go through the same material; not only will the process work, but the flow will be faster and ultimately what it was designed to be. So make sure to refer to your owner's manual and local gas availability, and pump the right kind of fuel into your 997.

Loss of Oil

While losing oil is never a good sign, in this case it could be a sign of carbon build-up. The reason being that as valves get stuck with carbon build up, they tend to move slower or even get stuck open, and oil can slowly leak through and be burnt when it shouldn't. There are two ways of finding this out. One way, if you do your own oil changes, is to notice considerable less oil than you originally put in. The other is to notice a lot of white smoke coming out the exhaust.

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