My 93 D150 2WD 5.9L started making this woof woof sound last night. It sounds like a freaking chopper lol. I'm pretty sure it's an engine misfire. I've replaced the air filter, plug wires, spark plugs, distributor cap, and ignition coil and it's still doing it. So I am starting to think it is a vacuum leak or something a little more internal. I'm no expert when it comes to mechanics I know how the things work and can do basic maintenance like brakes/tune ups etc. This is sounding like something I won't be able to fix myself unless it is something simple that I'm overlooking. Any suggestions before I go wasting hundreds of dollars to get something fixed that doesn't really need fixed?

 

Besides sounding different, does it feel different? Less power, shaking, etc?

 

Well, a few months ago it started jerking real bad around 55-60mph. It only used to do it once in a while when I first got the truck. I got the rear tranny mount replaced which fixed the vibration and jerk in the truck but it still has a little bit of a jerk to it. It still feels like it is running a little bit more rough usual.

EDIT: Could it possibly be the fuel filter?