I have a '97 Saab 900s 2.0 Turbo with 72000 miles on the clock. It is semi automatic with a manual stick and no clutch pedal. Recently it has started illuminating the ACS caption and disengaging the engine (the stick remains in the correct gate). This is intermittent and, after a few minutes the engine engages and allows me to drive on. I have taken it to my Saab dealer a number of times now, but each time it comes back with no fault found. I don't know how the system works, so I have no idea where to start. Any pointers?