I have a 92 blazer, 350 TBI, I replaced the brake booster and Master cylinder in it. Upon doing so, everytime you step on the brake the engine revs up and then when you let off the brakes it does it again. The pedal will go down the floor (not easily) when the truck is on but not when it is off. I have bleed the brakes..... no air in the system. I repaced the new booster (Reman) immediately and the issue is still there. one way check valve is good.

 

Does it idle normal or high when it's in "P" with no brake applied?
Check the vacumm hose from the check valve to the intake manifold, both ends.


It doesn't seem right that the brake pedal goes to the floor unless you have air in the brake system or a faulty master cylinder.
Was the master cyl reman also?

 

*Moving to Full Size Tech Section*

 

The rubber hose and steel line are both good, no leaks from the fitting in the manifold and yes the Master cylinder is reman also,,,, brakes have been bleed three times and are air free.