Jekyll & Hyde HDi

[Alan_M]

Are there any other symptoms when this happens?

Absolutely none.

Sluggish, MPG drops and chucks out dark/black soot on hard throttle.

Says to me that it's over-fuelling, so something is giving the ECU the wrong information intermittently. Absolutely fine yesterday and today.

I'm going to check the MAF and throttle potentiometer if the rain stops today. Other than that, how does temperature affect the HDi's? It's warmed up recently which coincides the car's improvement.