rough idling
I hve a 86 928 that has 99981 miles on it has run like a charm for 10 yrs with minor maintanence now all of a sudden its idling erraticly thrusting fron low to high rpms I tried adjusting the knock valve did,nt help i use high octain but because gas prices am using a cheaper gas,but still high octain I,m about install a new fuel filter if that does,nt work next will be a fuel pump,unless some one has a better and cheaper suggestion?