Try checking the u-joint bolts on the driveline. They need to be torqued at th e proper foot pounds. Or maybe clutch if it is a stick...
The brake pedal vibrates.
If the BRAKE PEDAL of your vehicle is vibrates, you need new brake pads or rotors, or both, and soon so you don't lose all brake power while you are driving.
Check for vacuum leak at brake booster
Most likely rotors are "out of round" and need to be either re-surfaced or replaced.
Sounds like a Vacuum leak in brake booster.
The PCM for the 89 Bronco is located on the firewall on the driver side. You can access it from inside the cab, behind the parking brake pedal.
Bad CV joint? How about a bad steering box?
Gasoline pedal/air intake pedal
Increase the driver's force on the brake pedal applied to the master cylinder
By driving and stomping on the pedal below .
look on the driver side firewall by the brake pedal
There can be many reasons so to why the pedal vibrates. You may have bad motor mounts, or the throttle cable mount can be loose. There is no sping located at the pedal, instread it is on the throttle body. Make sure everything is bolted down correctly and tightly