It sounds like you are describing oil smoke. Does this truck have an automatic transmission? If so, disconnect the vacuum modulator line from the engine and see if the smoke disappears after running for a while. Plug the vacuum connection at the manifold. If the smoke clears, the vacuum modulator diaphram is leaking and needs to be changed. Memory is foggy on this, but I think the ATs in that year still used a vacuum modulator connected to the intake manifold.
I don't think the PCV valve is the cause of your trouble, even though it may be stuck open. If the valve is as loose in the grommet as you say, there wouldn't be enough suction on the crankcase to draw any oil through the PCV circuit. But you could certainly get a rough or poor idle with the valve fully open.
Decent compression pressure for your engine would be 120-150 PSI, and more or less the same pressure in all cylinders. Much above 150 would be reason to suspect carbon buildup in the combustion chambers, which could be caused by ring or valve guide leakage. Much below 120 PSI for any cylinder would be reason to suspect valve leakage, or some other cause, depending on how much variation you find. Do dry and wet compression checks and let us know what you find. Do the dry check first, then give 2-3 squirts of oil from a pump oil can and check the compression in each cylinder again. Ring leakage will show up as an increase in pressure of more than about 20 PSI.
Also, check the color of the spark plugs. Dark and dry indicates the spark plug temperature is too cold, the causes of which may be slight oil consumption, rich fuel mixture, or the spark plug heat range is too cold- wrong spark plugs. Black and crusty, either dry or wet, typically indicates oil consumption, but with several possibilities.
Let us know what you find with the compression checks and the spark plugs.
Harvester
