The vacuum diagram for a 1998 Ford F150 is located in the service manual. It details how each vacuum line is routed, where the line is attached, and its function.
Follow the main vacuum coming from the intake manifold and it will right next to the vacuum check valve......
The schematics for a 2002 Ford F150 4x4 are located in various parts of the vehicle. The fuse schematic is located on the inside cover of the fuse box lid. The belt routing schematic is located on the front lip of the engine compartment. Other schematics can be found in Chilton's manuals for that vehicle.
More information. What help is rquired
You can find a 1981 Ford F150 manual transmission diagram inside the vehicle's owner's manual. Some auto stores also have the diagram available.
The vacuum at idle should be a steady reading between 17 and 22 inches ( in-Hg). for most automotive engines
depends on what you plan on doing if your doing mudding then bronco if your hauling things around and stuff like that then get an f150.
Chilton's manual, section 4.
Go to a junk yard and buy a used one.
The factory service manuals are the best source. You can find them on E-bay or other web sites. Chilton's, Haynes or other do-it-yourself manuals are not complete enough to carry these schematics.
Check your vacuum hose.