Check your vacuum hoses. If you have a leak, the engine control module (ECM) will react to the drop in vacuum and respond by accelerating the engine speed. Also consider the air conditioning system in the problem....does it occur when the A/C is on? Cycling of the A/C system may also be at fault.
Thank you, I have no A/C, this being a British summer I don't need it! I will get the hoses checked.
Hi, you might find that oil is leeking out of your turbo and getting into intercooler causing your engine to run on its own oil, remove the hose from the egr unit and check for signs of oil.