My son has a 2000 F150 with the 4.6 engine with about 120,000 miles. The truck is running rough when the engine is under load like going up a hill at moderate speeds. He has cleaned carbon out of the EGR valve and throttle body adapter. It was almost completely plugged. Have any of you had the pipe from the EGR valve to the exhaust manifold get plugged up with carbon? Also, do any of you know the size of the orifice in that line?
After cleaning the EGR he now has a SEL which Autozone says is showing a P0300 code which is very broad like random misfires. He changed the plugs about 15,000 miles ago.
Any help in pointing us in the right direction sure would be appreciated.

 

Mine ran like this without throwing a code. Felt like it wouldn't bull a greasy string out of a cat's butt. Ran compression tests and changed the plugs and fuel filter with no improvement. Checked the exhaust for excessive back pressure...it was fine, as well as the fuel pressure. Replaced the DPFE. A lot of the sluggush performance went away, but it still wasn't completely right, plus it started throwing the dreaded 0401 code. Started looking at the tube and orifice, but it seemed to be flowing o.k. Just for giggles, I tested the EGR valve itself, and sure enough, it was sticking open. I applied vacuum to it and shot marvel mystery oil to it, followed by carb cleaner, and the problems went away. I'll put a new EGR valve on it when I get a chance.