Hi, My 2007 RR Sport, a 4.4 V8 (not supercharged) has developed an intermittent fault which is driving me mad. Occasionally, and generally under no, or very low load, i get a warning message - "Reduced Engine Performance". It happens most frequently when driving down hills, when I've not been using the accelerator. Interestingly, other than very occasionally stalling as i coast up to a junction, you'd not know that anything was wrong with the engine.

I've taken the car to my local independent who have been very helpful, but are also baffled. Their clever machine isolated either the mass airflow sensor, or the accelerator pedal, which apparently has a device which tells the ECU how much throttle is applied. We've changed both, but on the way home today the message showed again.

Has anyone experienced this and if so, how did you fix it?

Help - please !!!!

As the RRS is very susceptible to electrical gremlins, I'd be tempted to look at the battery and alternator to make sure the former is healthy and the latter is doing its job properly.

I wonder if the fact that the issue tends to occur when the engine isn't doing much might point to the alternator failing to deliver when idling?

All just a pure guess but in the absence of a better idea... 2012 SDV6 - it's missing a couple of cylinders
2008 TDV8 - it was a labour of love and is much missed