I have a 1984 Ford F-150 4x4 stick with the 300 Inline 6 and it has asteady miss to it. When i downshift it sputters and has a steady miss to it. When it idles it also misses. It has new spark pluges and wires. It has just recently been timed. Any ideas on what is wrong with my motor. The air cleaner always has oil in the pan.

 

As for the miss.....

Could be any # of problems causing a steady miss. But the one that stands out in my mind is a burned exhaust valve. You'll feel the pulse in the exhaust when it misses. You could also have an intake valve that is not sealing, bad lifter, bad compression rings in one (or more) cylinders, leaky vacuum line,......Check the adjustment of your valves to make sure they are in spec (no lash!).

The oil in the pan indicates that your PCV valve has either bit the big one, the hose from the PCV valve is clogged, or the engine has too much blowby for the PCV system to compensate for.

Pull the PCV valve from the engine while still attached to the hose. With the engine running (at idle) you should feel a steady vacuum.(if you do your building too much blowby gases and the system can't keep up) If ya dont, pull the valve off the hose, you should hear a whoosh and the engine will either speed up, or stumble and die. If nothing happens, pull the other end of the hose off at the manifold. Whoosh?? The hose is clogged........Nothing???? the port is clogged.

Take a wire coat hanger and straighten out (leave little strategic bends in it). Run the coat hanger thru the hose
rotating the hanger while you run thru. Blow thru the hose.


Take a small flat screwdriver and scrape out the crud in the manifold port and flush port and hose and PCV valve out with carb claener. Check hose for cracks (or just replace it if its over 10yrs old).

Do some basic trouble-shooting.....compression(dry &wet)testing, vacuum gauge diagnostics, initial timing and advanced timing checks, go over the vacuum lines with a fine tooth comb, make sure carb is set to specs, etc.

Larry