Engine hesitation can be a result of low fuel pressure, vacuum leaks, worn or dirty spark plugs or bad spark plug wires. A weak ignition system can lead to misfiring, which can also cause hesitation.
Engine hesitation is usually caused by an air/fuel mixture that is too lean, meaning there is too much air and not enough fuel in the engine. This makes it hard for the spark plugs to create the combustion needed to sufficiently power the engine. This problem may be caused by a bad air flow sensor, a faulty throttle position sensor or poor computer operation. If the vehicle's computer is reading the signal from the air flow sensor incorrectly, it can cause the computer to fail to add enough fuel to the mix, making the mixture lean, and causing hesitation and drag.
It is possible to find out the cause of hesitation by running a few tests. Computer scans can pull fault codes, including misfire codes, and additional tests will help to check fuel pressure and find vacuum leaks. Pulling the spark plugs is another test that is easy and inexpensive to perform, since hesitation can be caused by a spark plug that is dirty or improperly gapped.Learn More
If an engine stalls upon acceleration, one likely cause is a dirty fuel filter. Not replacing the filter according to the manufacturer's recommendation allows debris from fuel to build up and plug it. This causes the car to operate on a lean fuel supply and render it unable to meet the demand of pressing the accelerator pedal, according to Carsut.Full Answer >
Restricted fuel delivery and malfunctioning spark plugs are the most common reasons for cars to hesitate during acceleration. The first step to identifying the cause of this is to find out if the car is fuel-injected or if it has a carburetor. Fuel-injected cars and cars with carburetors deliver fuel differently, so there are different ways to diagnose and fix problems with acceleration.Full Answer >
Dirty fuel injectors or vacuum leaks can cause a car to hesitate when the gas is pressed. It can also be caused by low fuel pressure.Full Answer >
A loose or slipping engine belt or a misaligned accessory drive pulley could cause a car to squeal upon acceleration. Engine belts and drive pulleys are used to power the water pump, air-conditioning compressor and the alternator of an automobile.Full Answer >