P0300 – Random/Multiple Cylinder Misfire Detected Audi R8

Audi R8 V 8 Misfire P0300

Shortly after buying the Audi R8 V8 the car developed a performance fault, when pushing the car to full-throttle, the R8 would stutter or misfire between 4,000-5,500 rpm. This started off as being intermittent, but after a while began to occur every time passing 4,000 rpm. The fault showing on the ECU most frequently was “P0300 – Random/Multiple Cylinder Misfire Detected”

The car reports and engine management light and would report the following errors codes during my experience of the fault over a month or two:

  • P0306 – Cylinder 6 Misfire
  • P0305 – Cylinder 5 Misfire
  • P0300 – Random/Multiple Cylinder Misfire Detected
  • P2293 – Fuel Pressure Regulator 2 Performance

This engine is similar to a B7 Audi RS4 if that helps some people with the troubleshooting.

Troubleshooting P0300 Misfire

Looking at any misfire issues there are a few basic steps.

Spark Plugs – A good step is to initially inspect the spark plugs and either clean or replace them. I replaced my plugs initially and cost around £12o for a set of eight good quality plugs. If the fault reoccurs you might want to look at the coils.

Coils – Remove and inspect the coils. Look for water damage or oil in the end of the coils. You can clean them with contact cleaner and replace. If the fault occurs with one specific cylinder swap two coils around and see if the fault moves with the coil to a new cylinder. If this problem doesn’t assist then you might need to look at a compression test.

In my case at this point my car stopped showing the misfire errors and started to report P2293 – Fuel Pressure Regulator 2 Performance. This lead me to look at the fueling of the car.

VCDS – I logged into VCDS and setup VCDS to log my misfires, it gives a lot more accurate data. From this I could see that there was more misfires than the ECU reports to the dash. All of the misfires were reporting to occur on bank 2. Which means it was unlikely to be a spark plug or coil issue.

From here I could use VCDS to look at my fuel pressures which were low once going over 4,000rpm.

Fuel Filter – I first replaced the fuel filter as this part is not scheduled for maintenance on this car at all. It has a built-in regulator and only costs around £25. This would be the first step for making sure the fuel is getting to the high-pressure fuel pumps without a restriction. The filter was holding a lot of dirt that I could see from when I drained the fuel back out of the dirty side of the filter.

High-Pressure Fuel Pump – Once the fuel filter was replaced, the issue was still occurring, just on bank 2. Next I removed the high-pressure fuel pump on bank two (this is the left-hand side looking at the engine). Opening up the pump you could see a dark black build up in the pump. I cleaned it the best I could using Redex and refitted it to the car.

The car then ran 90% better, but not perfect. This confirmed my fault. I needed a new high-pressure fuel pump.

P0300 Code – Cause on the 4.2-litre V8

The high-pressure fuel pump on bank 2 (left-hand side look at the engine from the rear). The pump appears to not put out the required pressure the car requires over 4,000 rpm. This starves the cylinders of fuel and displays as a misfire.

How To Fix P0300 Error on Audi R8 V8

To fix the issue I replace the high-pressure fuel pump on bank 2. The process is very simple and is accessible on top of the engine. I acquired a genuine pump for £305.

Here are some rough steps I took to replace the pump:

  • Disconnect the car battery.
  • Ensure the car is cold (a warm engine could increase the fuel rail pressure considerably).
  • Remove the fuel pressure sensor from pump.
  • Wearing eye and hand protection very slowly release the pressure from the pump by loosening the hoses
    • The low-pressure side has a clip that can be squeezed with pliers and the rubber tube slipped back.
    • The high-pressure side uses a 17mm nut, be very careful on this side to gently bleed the fuel pressure and ensure you catch the loose fuel with a rag and dispose of safely.
  • Once the pressure has been released disconnect the hoses.
  • Use a Torx bit to loosen the bolts that hold the pump to the car.
  • Once the bolts are out the pump can be lifted off and the new one replaced.

It is worth inspecting the cam follower on the car if it shows wear or play it might be worth replacing. In most cases on these engines, it should be fine.

When you next start the car expect it to take a little longer to crank the first time.

After replacing the pump the misfire was completely removed from the car and the P0300 fault hasn’t come back since.

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