There are many reasons why a car will not move when you step on the gas pedal and they vary from easily corrected to requiring a laborious repair. A lack of power often involves the fuel system in one way or another. It could be something as simple as an engaged emergency brake or as complicated as internal engine malfunctions.
A car that runs rough, is sluggish, or frequently stalls is dangerous. The first thing to do is ensure the emergency brake is disengaged. If the emergency brake has been eliminated as the problem, a mechanic is needed to diagnose the acceleration problem.
Common reasons for this to happen:
Acceleration issues typically stem from one of the following conditions:
- Emergency break is on or stuck: This is actually one of the most common reasons that a car will not move or seems to be experiencing poor acceleration. The brake may be on simply because the driver forgot to disengage it, or it may be stuck.
An emergency brake can become stuck if it is left on for a long period of time or if it was applied with more force than usual. In regions that use salt for de-icing, or when the emergency brake has gone without use for a long period of time, releasing the brake may require the assistance of a professional mechanic.
- Engine management issues: Many sensors interact with the engine control module to add the correct amount of fuel based on the amount of air that is coming into the engine.
As the engine management system wears, you may notice poor idle quality, stalling, and poor fuel economy. A car may run for months with a malfunctioning sensor, but eventually the problem may progress to a stalling condition or a serious lack of power.
A Check Engine light will normally be observed as well.
- Low fuel pressure: A fuel pump moves fuel from the fuel tank, through the fuel filter, and to the engine to be burned in the engine cylinders. If the fuel pump or filter begins to fail, lower than specified fuel pressure may cause various symptoms.
Symptoms of a failing fuel pump or clogged fuel filter may include sputtering, hesitation during acceleration, power loss when the car is under load, and finally an engine that will not start. Proper maintenance, including replacing the fuel filter as scheduled, will help prolong the service life of the fuel pump and maintain proper fuel pressure.
- Gross intake manifold leak: While this is not a common occurrence, a manifold leak does happen. This will cause the manifold to draw additional air via the leak, putting too much air into the cylinders and decreasing the amount of gasoline that is delivered in relation to air.
The engine will run rough and sluggish under such conditions. As the situation gets worse, it may eventually cause the car to stall. A hissing sound or Check Engine light may be observed as well.
- Malfunctioning electronic throttle control: Most late-model vehicles utilize an electronically controlled throttle to control airflow into the engine. This system relies on multiple electronic inputs, computers, and motors to control engine speed. If the system detects a malfunction, the computer will usually shut down the throttle opening as a precaution. In this case, multiple error codes will be logged, a Check Engine light may be displayed, and the vehicle may not exceed 35 to 40 mph.