my truck is 97 f150 with the 4.6. while tearing the engine down to do a headgasket i noticed that the lower intake had 1/8 inch of oil in the bottom. it appears to have entered the system through the PCV system. the engine has never used much oil, less than half a quart between oil changes (every 3000 miles) even with the leaking headgasket. what could have caused this oil to accumulate there. the truck has about 50 thousand miles on it. thanks.

 

Good and bad news. The good is that your truck has a fairly common problem. Oil coming in thru the PVC system seems pretty typical among many different vehicles. It is a problem for Mustang and Corvette owners as well as the Imports. If you do a Google search on "oil catch cans" or "PVC oil intake" you can get a better idea of what is going on.

The bad is that the oil eventually gets into the cylinders and the oil reduces the octane rating of the gas/air mixture which can contribute to detonation.

 

A faulty PCV valve can let too much oil into the intake. Also if the engine has a lot of blow-by, it can enter thru the throttlebody from the hose from the other valvecover.

 

could a plugged air filter cause the engine to draw more than usual through the PCV. a month ago the air filter became plugged when water and mud entered the air cleaner and froze. no water or mud appeared to have made it past the element. i am going to do a compression test on it to get an idea whats going on in the cylinders. what kind of pressure should i expect to read. also i have noticed lately that it does ping/detonate more than usual.
if this accumalation had gone unnoticed, but the problem corrected, would the oil be stuck in the intake or would it eventually clear it self out.

also where could i find the torque specs and sequences for the heads, intake and spark plugs
thanks.

 

That could have caused it. It would take a long time to clear itself out.