Saab 9000, 1996 causing a bit of a problem. On start-up, idle can be erratic and engine sounds as if its missing badly. Most times it settles down to normal idling and engine note improves. However, it can also happen when driving causing fuel consumption to increase dramatically and a loss of power. Is this a ECU problem or am I missing something? Car has 130K so don't want an expensive fix. Ideas please?