We bought our son a 1.0 Corsa 53 Model, 70,000 miles. Since we bought it 4 weeks ago we have had it fully serviced, a new timing chain had to be fitted and a new crankshaft sensor, but still the car, when it gets warm makes a high pitched whine and then at traffic lights the engine slows and it continues to make a low pitched whine, to the extent that the instrument lights start to dim and the car almost stalls. What could now be going wrong?, the private mechanic appears to know the engine and says he has fixed many of them, but so far he doesn't seem to be able to solve this one, is there anyone who can advise us, before we give it to Vauxhalls and have to spend a lot more money, which as pensioners we don't really have.