1999 Ford F-150 5.4L V-8 with roughly 221,000. Bad Misfire at Idle and when driving, and very harsh chug when accelerating. Hasn't thrown any codes yet. also has a whine/whirl noise coming from engine, not from belt. Found oil deposits below intake manifold, and can see excessive smoke from tailpipe. Engine smells rich, possible fouled plug (oil residue on back right ignition coil pack) Misfire isn't as harsh at idle, but still noticeable, gets bad about 1,000-2,000 RPM, also isn't bad when not under load (going down hill or flat ground) When accelerating entire vehicle shakes, chugs, lack of power.

My first thought was spark plugs and vacuum leak. (possible plug coil, intake gaskets, vacuum lines) Couldn't tell if smoke was white or not (dark outside) but had a coolant smell to it. Im not familiar with ford intakes and was wondering if they have coolant passages. Any information would be helpful, past experiences with similar symptoms and fixes. Thanks.

 

Have you ever changed the plugs?
Have you scanned for pending codes?
Until you do something, it's just guessing.
Likely need coils at this mileage.
Gooed luck.

 

Is your coolant level lower than normal? There is a coolant passage through the manifold but it never passes along side any of the intake runners. If you have a coolant leak, I think your intake manifold gaskets are more likely the culprit, hopefully its not a head gasket.

The other thing that comes to mind is sometimes water can get past the coil boot seals and effectively short that spark plug out. If this is the case, you will be able to tell if you pull the coils and inspect them for moisture.

At 221.000 mi, it sounds like you're probably due for new plugs and maybe coils anyway.