UK Car Repair: vaux astra 2000 dti, fuel air mixture, replacement turbocharger

Question
QUESTION:  losing power on the motorway. then today i got in car and it sounded like the fan belt was playing up but i had to keep driving on motorway, by time i got home the car was revving up on its own and by the time i pulled over there was smoke coming out from exhaust, badly. any ideas.

ANSWER: Hi Gina ,Is there an orange light on on the dashboard (a picture of an engine with a lightning flash through it) if so you need to get a vauxhall dealer or a good garge to run a diagnostic test to read codes ?.It could just be a stuck open EGR valve although There is a slight possibility your turbocharger oil seals have blown as this introduces oil into the engine and causes heavy smoke and loss of power. What colour is the smoke ? (blue indicates oil burn). When you say fan belt do you mean squealing at raised engine speeds? (bearings in the turbo running dry due to lack of oil feed). A replacement turbocharger can be extremely expensive so before you change it check the oil feed to it and the crank case ventilation for blocking and the throttle body for oil deposits as these can also cause smoking . If you start the car now does it squeal when you raise the engine speed and is it still revving on it's own? , Hope this helps you let me know -thanks Paul

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QUESTION: when my son tried it 30 mins after it revved straight away very high without him touching the accellerator, throwing out alot of dark brown smoke, then when he turned the engine off it took atleast 3 mins for the engine to stop revving and cut out????

Answer
I would turn my attention to the ER valve first of all. You don't mention if there are any lights on or not as this would be very helpful indeed because if the light is on your engine control computer can be scanned for codes to say exactly what the problem is.the deal with a diesel engine that no ingnition is required for combustion as it uses only compression of the fuel air mixture. The only thing that stops a CI engine (combustion ignition) is a solenoid in the top of the fuel distributor pump which cuts off the fuel. The EGR valve basically recycles exhaust gases from the engine (can be used as fuel)if the engine  is not running 'clean' it will clog up quickly it could be any number of things causing this, the fuel you are using for instance. When was the fuel filter/air filter last changed? as this can cause the EGR to stick open.-  hope this helps you - Paul