What is the point of rev hang?

Rev hang is a delay in engines revs decreasing when you lift off the throttle. It occurs on most modern internal combustion engines, but is more noticeable on manual transmission equipped cars because you are in complete control of shifting.

Why then do you need to keep the engine running and the gas pedal pushed down?

It’s all about the timing and “balancing” the clutch. If you push down on the gas pedal too quickly, you’ll rev the engine, and if you take your foot off the clutch too quickly, you’ll stall.

What happens when you push the throttle?

As the gas pedal is pressed, it turns a pivot that in turn pulls the throttle wire. The more you step on the gas pedal, the wider open the valve becomes and the more air is let in. Various sensors monitor this airflow and inject fuel accordingly to maintain an optimum ratio of air to fuel.

Is it bad to rev your engine with the clutch in?

Yes it can damage the clutch release bearing. If you do it excessively. It will also put strain on the crankshaft thrust bearings. So just don’t do it.

Can a vacuum leak cause rev hang?

Check for small vaccum leaks b/c they can slow your throttle response. Check your dv’s diaphragm and make sure it isn’t sticking open. If it is a clutch problem, it will most likely get worse over time and the RPM hang will start to become more “dramatic” so to speak.

Why rpm goes up and down?

It sounds like you have a dirty or failing air control valve. The job of the idling air control valve is to bring this deceleration down to a slow and smooth idling rather than cutting off the fuel supply and causing the motor to die. …

Why does my truck keep dying when I let off the gas?

If the engine runs fine when you are holding the accelerator pedal down and dies when you release it then you may have a couple of possible issues. If it is dirty it can starve the engine of air at idle. If nothing turns up there then you may have a bad idle control valve or air flow meter.

Why does my truck shut off when I let off the gas?

The car will stall if the valve is too clogged or when it finally fails. If, while holding the accelerator pedal down, a small amount of pressure keeps the car running at a stop, the idle control valve may require attention. In most late model cars, this problem will usually trigger the Check Engine light.

What causes engine idle speed to be high or low?

What Causes Engine Idle Speed to be High or Low. On a modern fuel injected engine, engine idle is controlled by the engine control unit (ECU) and an electrically operated throttle control module. When the idle is high or low, it could be caused by a malfunction of this system or any of the individual components that comprise the system.

What causes a car to stall at idle while driving?

When idle speed changes significantly or stalling on throttle release occurs, a problem is indicated. Most often an input sensor has failed or the throttle body has a problem. On later model vehicles, a check engine light may accompany the issue.

What happens when a throttle bore is damaged?

When it’s damaged, more air can pass through, which will cause the engine to idle high or low. A damaged throttle bore will result in the same problem, because it’s no longer able to regulate the volume of air flowing into the engine.

How is idle controlled on a fuel injected engine?

On a modern fuel injected engine, engine idle is controlled by the engine control unit (ECU) and an electrically operated throttle control module. When the idle is high or low, it could be caused by a malfunction of this system or any of the individual components that comprise the system.