I have a 1999 f250 with a 5.4 5 speed. Has 127k miles. The knocked started going down the highway, before the knock it was gutless then it started. On th way home my oil pressure would bounce sometimes. I can start it up, and it will idle smooth, somtimes it wont start unless i give it gas and the rpm drop as low as 500 at times. Ive checked vacume lines and changed the oil, still nothing. Any suggestions?

 

Use a scanner to see if there are any codes.

 

check for loose spark plugs.