* Engine vacuum leak: The brake booster uses engine vacuum to assist braking. A significant vacuum leak can cause the engine to increase its idle speed (rev up) to compensate, and the brakes may feel weak or spongy.
* Brake booster malfunction: The brake booster itself could be failing. It might be leaking internally or have a faulty diaphragm.
* Throttle cable or linkage issue: A sticking or binding throttle cable or linkage could cause the throttle to slightly open when the brake pedal is depressed. This is less common, but possible.
* Faulty idle air control (IAC) valve: This valve regulates air entering the engine at idle. A malfunctioning IAC could lead to increased idle speed, possibly triggered by something related to the braking system (although this is a less direct connection).
* Transmission issues (automatic): While less likely, a problem in the transmission's control system could lead to the engine revving in response to braking, particularly if there's a linkage between the transmission and brake systems. This is relatively rare.
* Improperly adjusted or damaged throttle position sensor (TPS): This sensor monitors the throttle position. A faulty TPS could send incorrect signals to the engine control unit (ECU), leading to unexpected engine behavior.
It's crucial to not drive the vehicle until the problem is diagnosed and fixed. Driving with this issue could be dangerous, as your braking performance might be compromised. Take it to a qualified mechanic immediately to have them diagnose the cause of the revving engine when braking.
