My '86 with a 2.8 (255,000 mi) has developed an annoying spark rattle/knock when pulling a grade for a while, and sometimes just after shifting.
I have no error codes.
I read in another post that the MAP sensor may cause this type of problem. I did a vacuum test (mouth on longer hose), and discovered that mine does not hold a vacuum! Should it?
All other elements seem to be fine. Power is ok for a 2.8, just this annoying rattle/knock under load. I run 89 octane, unless I know I'm going to work it, then I use 92..
Thanks for the help.