ENGINE TROUBLE: Diana Godelman of Northridge took perfect care of her 1991 silver Honda Accord, which is why it was at Woodland Hills Honda for a tune-up. But when her husband, Alex, went to pick up the car Friday, paying for the repairs first, there was a problem: The car was missing. It had been stolen off the lot, said service manager Marion Calvin. Its remains turned up later. . . . No tires. No front seats. No need for a tune-up.