Problem of misfire on a 2008 Audi S5 with a 4.2 V8 engine.

[CelestialSeeker]

Greetings, everyone,

I have a 2008 S5 4.2 V8 that is performing poorly. The car starts without any issues, but, it runs unevenly and the Engine Malfunction Indicator Light (EML) is flashing.
The codes are listed below.

The diagnostic code P0300 indicates the detection of several misfires.
The code P0018 indicates a fault in the position of the camshaft in the specified bank. The user's text is "2 A".
The engine is experiencing a misfire in cylinder 8, indicated by the code P0308.
The engine is experiencing a misfire in cylinder 7, indicated by the code P0307.
The engine is experiencing a misfire in cylinder 5, indicated by the code P0305.
P0306 indicates a misfire in cylinder 6.
The engine diagnostic code P0304 indicates a misfire in cylinder 4.

Up till now, I haven't attempted anything. However, I am planning to start soon. Before doing so, I wanted to get some advise.

We would much appreciate any guidance or recommendations.

Thank you, everyone!

[CelestialSeeker]

Is there anyone available to help?

[Gianni682]

What is the distance in miles? Can you provide information about the service history? What tools or methods did you use for the required scan? VCDS Ross Tech is a software program.

[CelestialSeeker]

Thank you for responding. The vehicle has a service history that is documented till 2022 and has travelled little over 100,000 kilometres. I used a snap-on diagnostic scanner to get the codes.

[Gianni682]

Understood. I acknowledge that the Snap-on tool is of high quality, however it is possible that the VCDS offers more advanced features.

[CelestialSeeker]

Very well, I have a friend that has VCDS, so I will ask him to examine the issue. Today, I removed the input manifold and discovered a significant accumulation of carbon. Could this potentially result in such a problem?

[CelestialSeeker]

Alternatively, may the issue be attributed to the camshaft sensor? Is there any method to do a test for it?

[Gianni682]

These engines are renowned for carbon accumulation, which, if left uncleaned, may certainly lead to issues. Begin by taking one step at a time and have the engine undergo carbon cleaning as a first step. Temporarily refrain from manipulating the sensor and avoid making many modifications simultaneously without doing proper testing.

[CelestialSeeker]

Indeed, the carbon cleaning process has been successfully completed. The automobile is marginally superior... The automobile is able to idle, but it does so in an uneven and harsh manner. Additionally, when the car is revved, it still has repeated misfires in the main cylinders numbered 5 to 8. The car's performance seems to improve somewhat after it reaches operating temperature. I have inspected the plugs and other components, and everything seems to be in proper working order. What are your recommendations for my next course of action?

[CelestialSeeker]

A compression test was performed and the results indicate that everything is in good condition.

[Rudy7831]

If you are using the original injectors, it is advisable to consider changing them. It seems to be a frequent problem that arises after individuals have removed carbon buildup and continue to have difficulties. Swapping plugs and coils is a simple way to determine whether the problem persists, however addressing injectors requires accessing them behind the manifold, which is more complicated.

[CelestialSeeker]

Removing the manifold was a painful experience that I did not find enjoyable. Do injectors not trigger an error code? After completing another scan, I have also detected code P1575 indicating a short circuit to the positive terminal in the right engine mount. Is this a potential factor contributing to the misfires?

I am grateful for the assistance, gentlemen.