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Carbon Buildup on Intake Valves
Audi and other manufacturer's first generation attempts at direct injection yielded increased horsepower and greater fuel economy. With direct injection however there comes a dirty secret which is carbon fouling of the intake valves.The 2.0T motor in the A4 employs direct injection to place fuel precisely into the combustion chamber. Unfortunately, this means that fuel does not pass through the intake manifold and past the intake valves with its solvent cleaning effect. The result of this buildup if it becomes severe enough is a hard start condition, poor idle and misfires. We plan to pull our intake manifold shortly and assess the condition of our engine. There's no mention of a cleaning having been performed in the service history of the vehicle so we could be in for a treat!
The tumble valves will be similarly coated in carbon grime and will require a good soaking to come clean. To our knowledge no carbon cleaning service has ever been performed on our car so look for a thorough write up when we tackle this job! Thanks to Jim robbington on audizine for the images.Diverter Valve Failure
We don't have a picture of ours but here is a torn diverter valve from jake@jhm on audizine. Diverter valves should be replaced with the latest “H” revision or an option from the aftermarket if they fail.The diverter valve is bolted to the compressor of the turbo and regulates boost. Failure of the unit is sometimes accompanied by a whistling sound under boost and reduced boost pressure. Early versions of this unit used a diaphragm and were prone to failure. By now many of the will have been replaced. Though are unit showed no evidence of failure we have upgraded to the piston type unit as our local Volkswagen dealer had one available at a good price one day while we were at the parts counter.
What Comes Afterwards?
APR is one of several reputable manufacturers producing ECU tunes for the 2.0T.Once we've finished getting our car in tip top shape with a carbon cleaning we can move on to upgrades. So with a car that's running right and ripe for upgrades what will be first on our agenda? More power of course! Several reputable companies produce ECU tunes that allow for an additional 40 – 50 horsepower on an otherwise stock engine. This feels to us like the amount of power that the car should have come with from the factory so it seems a good place to start.
034 Motorsport produces several suspension components that we wouldn't mind investigating further.After we have a power increase under our belts we can look at sharpening the handling of our project. The same handling abilities that exist in the S4 are baked into the chassis of our A4 so with a few select upgrades there we should be able to easily out handle a stock S4.
