1988, approx 150,000 mi. Rarely leaves the yard. Seldom driven. Starts instantly but barely idles when cold. Somewhat better when hot. No power. No codes. Good ignition on all 8 but sounds as if it is running on less than 8. Vac about 9 in. at idle. By carefully pumping throttle will increase to 2000 rpm with severe back fire. Will some times get to 3000 rpm. Vac drops to zero above 2000 rpm. and, momentarily, jumps to over 20 in. at deceleration.
Have used two cans carb cleaner searching for vac. leak. Could find none. Because of little use, treated both oil and gas with no effect. Have not yet checked compression. Cat was removed years ago. EGR was sealed off years ago. Ran very well until recently.
Thanks bent-1. Good thought. Did not know that could happen. Of course, the old girl is a lot like me. After 80 years, my timing is a little off too. Yes I have a light and will check it out. Puzzled why I get no codes.