Tacho freaking out then won't idle

[Pj-14]

Hi have a 2006 diesel wagon only a week old, drove great for first 150 k's road and fire trails. Tried out all the interior buttons only thing I had done differently prior to problem is turn on the pre heat button and fill coolant tank, now5 minutes after driving the tacho starts fluctuating past the red zone then car wont idle and stalls, takes a few go's to start it then engine light stays on and back to normal. Have looked through some threads on here and have taken battery off for 30 mins and emptied fuel filter. Any other suggestions welcomed before I take it to mechanic for a fleecing.

Thanks Pj