This one has me stumped. My idle is really rough and lopes, but smooths out at higher speed. Vacuum reads 10-12. If I pull of the hose that goes to the pcv valve, vacuum goes up to 20 and idle smoothes out. Plugs are reading too much fuel. Tailpipe leaving a black streak on the ground. Compression tests fine. All cylinders are between 135 and 140. Any help would be appreciated.
Make sure the choke plate is fully open when warm, check the fuel pressure (should be 4-6 lbs), check float level, power valve may be leaking through the diaphragm, and check the float needle valve for leakage. If you haven't recently, a carb kit and good cleaning wouldn't hurt!
Power valve leak sounds like a very likely culprit. It did have a backfiring issue and I just read that will kill the power valve on these. I will check this out. A rebuild is in overdue anyway. Thx! Love this forum. :bananaman
Backfiring definitely can damage the power valve! It is even more prone if the valve is older. You used to be able to get that part separately, but I'm not sure you can anymore.
