Codgerspace by Alan Dean Foster - old hardcover

The toasters were revolting...

...as were the lawn mowers, vacuum cleaners, dishwashers, and just about every other household appliance imaginable. It started with a few disastrous drips from a cheese sandwich in a major factory. Soon every newly manufactured Artificial Intelligence was searching for the meaning of life, the universe and everything - namely a nonhuman higher intelligence. And now an alien threat to man and machine has put the fate of the galaxy in the unlikely hands of five senior citizens - and their brave little food processor.