Brake Pedal/RPM's

Sometimes when I am at a stop light the engine in my 2002 Chevy Trailblazer seems to lose rpm’s, shudder and the brake pedal moves down a little bit. Any ideas what might cause that?

You might have your power brake booster, a vacuum device, checked for a leak…

Ok, Thank You!

Yes, you probably have a vacuum leak, most likely in the brake booster.