Why does the Lavida's engine speed increase when braking at idle?
3 Answers
It could be due to the transmission downshifting, causing a momentary increase in torque, which should be a normal phenomenon. It is recommended to visit a 4S shop for inspection or compare with the same model. Normal phenomenon: When driving at a constant speed on flat ground, pressing the brake causes the engine speed to rise to 1500 rpm and then drop to 1100 rpm, maintaining at 1100 rpm when stopped: this is because the increase in speed leads to an upshift, and pressing the brake causes the speed to drop, leading to an automatic downshift, which increases the engine speed. This situation is quite normal. ECU receives deceleration signal during braking: When the vehicle is braking, the ECU receives a deceleration signal and will automatically downshift according to the speed to provide additional engine braking. Most engines have a minimum fuel cutoff speed around 1100 rpm, so before the current gear's speed drops below 1100 rpm, the transmission will downshift in advance to prevent stalling.
As a seasoned driver with years of experience, I've encountered a similar issue before. That time, when I stepped on the brake at idle, the RPM suddenly surged to over 2000, which scared me into shutting off the engine immediately. Upon careful inspection, I found that the vacuum booster pump's hose was leaking. The brake system relies on vacuum to function, and a leak causes the engine to draw in more air, leading to increased RPM. Ignoring this minor issue could result in reduced braking efficiency, potential damage to engine components, and increased fuel consumption. Nowadays, vehicles rely on electronic controls, and if the idle air control valve gets dirty or stuck, it can also cause trouble. An improperly transmitted brake signal can mislead the ECU into increasing RPM. My suggestion is to have it checked at a professional shop where they can use diagnostic equipment to quickly identify vacuum leaks or sensor failures.
I remember once at a repair stall, the owner briefly checked my issue of RPM rising when braking. He said many car owners overlook the pipes around the brake booster – aging or cracking causes vacuum leaks, increasing air intake and thus raising RPM. It's best to start simple: listen for hissing under the hood and check if idle is stable. In big-city traffic jams, this problem is more annoying, potentially affecting AC cooling efficiency or accelerating brake pad wear. The stall owner recommended regular air filter changes and throttle body cleaning to reduce such issues, saving money and ensuring peace of mind.
