Our 940, no turbo, will surge for no reason (idles at 800rpm and goes up to 1700 rpms). It will actually push you at a red light if your foot is not heavy on the brake. It did it today, soon after starting and before the engine got very warm. Ususally it is after driving a while and engine at full running temp. I read about a similar problem and he found a rear, second temp sensor was bad. I'll replace that this weekend. Someone also suggested that I clean the idle control unit. That makes sense too. Are there any suggestions. thanks