Originally Posted by tyl604

OK - you are talking about the rubber bumpers. Now I see. I have been replacing these for 35 years on my 81SD and have never seen any effect on the idle. In fact I do not buy new ones any more; I drill a hole through the bumper after removing the top and bottom metal screw and plate and insert a long bolt through the entire bumper. Now instead of replacing about every six months to a year, I just about never replace them.

My idle goes from rocking at one stoplight to smooth as glass at the next stoplight to rocking again. Have never been able to figure out why. At some point something just kicks in and it idles smooth as can be but no idea what it is.

But I am pretty sure the buffers/bumpers have no effect on the idle.