Movement in brake pedal when starting car?

[Boostdtalon]

It just started this today. When I start the car the brake pedal will fluctuate. It will move towards the floor but no more than an 1/8 inch and than immediately return. Brake fluid levels are normal and I had the brake pads and rotors replace over a month ago. There are no other issues with the brakes. I'm not sure how I should go about investigating this. I'm thinking maybe its something to do with the ABS. /ubbthreads/images/graemlins/dunno.gif Anyone ever dealt with this issue?

 

[bmod530]

As soon as you start your car your brake booster receives a vacuum, decreasing pedal effort. Should be a normal symptom. 1/8" is minor.

 

[Boostdtalon]

Guess I never noticed it before. hmmm I haven't really been driving the car lately.

 

[bmod530]

If it functions normally afterwards I don't see a problem. One test is to pump the pedal up until it is hard *with the car off*. Then when still keeping a heavy foot on the brake pedal, start the car. Should receive normal vacuum from your description and become operational.