In attempting to diagnose the rough idling of my '91 940 2lt non-turbo auto, I came across a worrying anomaly. The timing is around 30 degrees advanced on idle. The timing increases on revving the engine to around 60 degrees... The Haynes says it shoud be advanced only 10 to 12 degrees on idle, but I cannot find a way to adjust this! The only symptoms are a rough idle - the revcounter dips and returns from 850 to 650 and back, and frequent stalls in traffic queues. any thoughts ?? I think I have ruled out : The Idle control valve The Timing belt The ignition system as a whole, inc plugs, leads and rotor/distributor The fuel supply - new filters and both pumps ok The crank case breather What is left ?????