What Causes Cars to Lose Power When Trying to Accelerate?

Bjorn Vinter/UpperCut Images/Getty Images

A car loses power during acceleration if it doesn’t have enough fuel or lack of power to the system. It can be difficult to pinpoint the exact cause, but it’s likely a fuel system malfunction.

Insufficient Fuel Delivery

A car with a healthy fuel supply should respond quickly when the owner depresses the accelerator. If stepping on the accelerator does not trigger a quick response, there is a problem with fuel delivery. There are several possible causes for impaired fuel delivery, including clogged, damaged and defective parts.

One common cause of insufficient fuel delivery is a clogged or malfunctioning fuel injector. Over time, the small passageways of the fuel injector can get clogged with dirt and other impurities. As a result, fuel supply to the injectors is limited. This causes slow acceleration or stalling. A decrease in fuel economy can also signal a poorly functioning fuel injector.

A defective fuel pump can also cause similar symptoms. The fuel pump brings gas to the engine via fuel lines. If the lines get clogged, the vehicle can accelerate slowly or hesitate and stall. Impaired fuel delivery can be traced to a clogged filter, too. The fuel filter works by cleaning out impurities in the gasoline. If it gets clogged, less fuel reaches the injectors. Since they can clog easily, fuel filters should be checked regularly.

The fuel supply can also be interrupted by a dirty airflow sensor. These sensors detect how much air a car intakes, and they relay a message to the car’s computer system that triggers the release of the corresponding amount of fuel. When the airflow sensor gets dirty or wears out, the car’s computer receives inaccurate data.

A leaking fuel line is another cause of poor fuel flow. With a crack in the fuel lines, gasoline will not reach the injectors. The smell of gasoline or a puddle under the car are indicators of this issue.

Another source of impaired fuel delivery is a vacuum leak. When this happens, the car’s computer system has trouble maintaining a proper fuel-to-air ratio. In addition to slowing fuel delivery, a vacuum leak may trigger the “check engine” light to come on.

Finally, a failing catalytic converter may reduce fuel delivery by preventing the proper amount of air from reaching the engine. In addition to accelerating slowly, the car may be hotter than normal.

Lack of Power

Loss of power is also attributed to several causes, most of which arise from the exhaust system. Misfiring spark plugs and bad cylinders can rob the car of its power supply, as can antifreeze or oil entering the exhaust system. If power loss comes from misfiring spark plugs, the degree of power loss corresponds with the rate of spark plugs misfiring. Left untreated, the problem gets worse. Misfiring also increases exhaust emissions and robs the engine of power.

Overheating frequently damages cylinder heads, which may lead to a head gasket failure, and an improperly functioning head gasket may lead to cracks in the cylinder head. A classic sign of a cracked head gasket is white smoke coming from the exhaust pipe, which means that coolant fluid leaked into the exhaust system.