What causes a sudden high RPM when shifting to N gear?
1 Answers
Below are the specific reasons for a sudden RPM increase when shifting to neutral gear: 1. Faulty charcoal canister purge valve: When the vehicle is shifted to neutral, the engine returns to idle state, and the charcoal canister purge valve should close. If the valve fails to close or doesn't seal properly, fuel vapor from the charcoal canister will continuously flow into the intake manifold and enter the combustion chamber, causing a sudden RPM rise in neutral. 2. Faulty vacuum sensor in braking system: With a malfunctioning vacuum sensor, the system cannot detect whether the vacuum level in the brake booster is sufficient. In this case, the engine will increase RPM to enhance its suction power, thereby raising the vacuum level in the intake manifold.