Dazed and Confused
Join Date: May 2012
Location: Upstate New York
Re: 1978 Mercury Grand Marquis Specs
Sounds like your neutral safety switch has either failed or out of adjustment. As far as the reverse situation, I'm wondering if you may have a vacuum leak, coming in and out of OD might be due to that as well, I believe it was still vacuum controlled then.
Ever notice that there's so many high performance parts available for GM products?
Did you ever think that maybe they NEED them?