Brake pedal moves

[drmopar69]

Any ideas? I start my vehicle and the brake pedal lowers and turns on the brake lights. While driving, I’ve noticed while slowing down/deceleration the pedal moves toward the floor. During acceleration, the pedal moves up toward the brake switch…I’m thinking either the booster is leaking or the master cylinder is bad. Brake lights stay on all the time while driving, shut off the car and use foot to lift the pedal to shut lights off…

[EasyRider300M]

How to test the booster:

[FIREM]

First, adjust the brake light switch.
1) Depress brake pedal
2) Pull the inner plunger out of brake switch
3) Release the pedal and allow it to set the switch
DO NOT PULL THE PEDAL UP
Road test
Your “unusual” pedal movements may be due the the brake light switch and ABS Cycle function out of sync

ABS Cycles at various times during drive cycle that is usually not detected but could cause pedal movement. There are notes in the owners manual about this.

[drmopar69]

My ABSTRACT Light are on, I believe it may be a wheel sensor? Will that make my brake pedal move during acceleration/deceleration?

[FIREM]

Yes, no doubt that would cause the pedal issue. You will Ned a scanner capable of reading ABS codes. Key dance won’t give codes other than engine& emissions

[drmopar69]

I had a huge hole on the bottom of my brake booster, after replacement, I can push my pedal around 2 inches and get brakes!! Total difference.

[In-trepid]

You should only have to push the pedal about 3/4 of an inch before you get brakes. Sounds like the adjuster on the booster that actuates the master cylinder isn't adjusted right. I had this same issue when I replaced a booster. turned it out two turns and it was perfect. It's east to do as all you have to do is remove the master cylinder (two nuts), pull it out a bit as the brake lines are flexible, and make the adjustment. It will probably take more time to remove the cowl pieces and strut support than doing the actual master cylinder and adjustment.