PCV Valve Vacuum Leak

[Robert Crandall]

I bought a 1978 C20 292 I6 4-spd manual new in January, 1978, and I still use it.

Often, since new, when the motor is hot it shakes horribly at idle. The problem is that the PCV valve ball sometimes does not get sucked up tight which causes a vacuum leak and the shake. There is plenty of vacuum. Plugging the end of the PCV valve with my finger fixes the vacuum leak to demonstrate what is wrong. Removing the valve from the cover and turning it sideways drops the ball into place to make it work also, and it stays in place when reinserted into its hole. Replacing the PCV valve fixes nothing. Buying cheap or not so cheap ones also makes no difference. Besides being annoying, the shaking loosens the connection to the exhaust pipe which makes that joint leak.

There are probably millions of these cheap little valves in service, so they must actually work. Does anyone how I can fix this? Thanks.