Rough idle @ economy guage not working 420 SEL
I lent my 1988 420 SEL to my father inlaw and when I got the car back the idle was rough. He had filled the car with gas so my first thought was bad gas. I have already run Three quarters of a tank of new gas through the car and it is still idling rough. I also noticed that the economy gauge had stopped working. Could a vacuum leak cause a rough idle?