More brake is applied when stopped, RPMs go lower

[tophattwaffle]

Let me pre-face this with I know almost NO knowledge of cars inner workings, please be nice...

So I started to notice this today when driving around town today. When at a red light, and fully stopped is when it happens. It seems that the more I apply the brake when stopped, the lower my RPMs are.

Once the pedal is depressed to a certain point the RPMs are around 600, and the steering wheel starts to vibrate a bit. Then once I start to drive it seems to jerk a bit (Possibly shifting gear? I don't know.) If I slightly apply the brake, my RPMs are around 850 and there is no shaking.

I'm wondering if this is normal or not?

[white89gt]

I think what you are experiencing is this.... Your brakes use engine vacuum to assist you so less pedal effort is required from you. The harder you push, the more vacuum it is pulling. That is putting a strain on the motor, which in turn lowers the rpm's. The shaking is caused by the motor being at a lower rpm, from my experience 4 cylinders are a lot more finicky as to where they like to idle.

I have an '06 Escape that will produce the exact symptoms you describe. It also shakes when the A/C compressor kicks on when it is at an idle.