What Causes Engine Idle Vibration After Hard Braking?
2 Answers
High-speed driving followed by braking to decelerate causing engine vibration is a normal phenomenon. Introduction to Idle: When an engine runs without load, it is called idling. During engine operation, if the accelerator pedal is completely released, the engine enters idle state. The rotational speed during engine idling is called idle speed. Idle speed can be adjusted by modifying parameters such as throttle opening. Generally, the optimal idle speed is the minimum RPM at which the engine does not vibrate. Function of Idling: Avoiding wasted work - Idling overcomes the engine's internal friction to maintain minimum rotational speed, providing convenience for drivers during various driving conditions and temporary stops. For instance, when waiting at traffic lights or in congested traffic, although the duration may be brief, temporarily turning off the engine can achieve immediate energy-saving and emission-reduction effects.
That day I had just come off the highway and had to slam on the brakes to avoid a rear-end collision. After the car came to a stop, the engine started shaking violently, which really freaked me out. A friend had once told me that during hard braking, the vacuum booster sucks a lot of vacuum from the engine. If the hoses are old or leaking, it can cause insufficient vacuum and mess up the idle. It could also be carbon buildup clogging the throttle body—the braking vibration might have exposed the issue—or dirty spark plugs causing intermittent ignition. I went to get it checked right away, and sure enough, it was a leaking vacuum hose. Replacing it with a new one fixed the problem. Just a reminder: cars that frequently go on long trips tend to accumulate dust, so regularly cleaning the engine bay can help prevent issues. Don’t wait until the shaking starts to realize there’s a problem.
