Why Does My Car Hesitate When Accelerating?

Reasons Your Car Hesitates When Accelerating, And How To Fix It

Check engine light illuminated on the dash board of a car

Reasons Your Car Hesitates When Accelerating and How to Fix It

Hesitation when accelerating can be caused by several different problems, but the symptoms are all similar. A delay when you press the gas pedal, sluggish driving, and jerking or sputtering when you try to speed up are all symptoms that point to a bigger problem with your engine. Each of these engine trouble symptoms are typically accompanied by a check engine light, either solid or flashing, depending on the severity of the issue. Engine hesitation is a problem that normally gets worse over time, and can cause internal damage to the engine if left unchecked. At Jamie’s Tire & Service in Dayton, Ohio, we repair vehicles with these engine problems daily, and today we’re going to share several of the top causes of sluggish acceleration and how we fix them in our auto repair shops.

Common Causes of Engine Hesitation

Dirty, Clogged, or Broken Fuel Injectors Cause Driving Issues

Modern gas engines in cars and trucks rely on fuel injectors to provide gas or diesel to each cylinder to keep your car running smoothly. Each injector fires a small amount of fuel into the combustion chamber, where it is ignited by a spark plug. Over time, these fuel injectors can become clogged or malfunction, which keeps them from being able to provide the correct amount of gas at the correct time to your car. These problems often present themselves as a “misfire” or stalling, as well as hesitating to accelerate. Fuel injectors clog due to debris in the fuel and buildup from many miles of driving. While it’s less common, fuel injectors can also physically break, which stops them from working correctly.

Faulty or Worn-Out Spark Plugs and Coil Packs

The second of the three components an engine needs to function is spark. Spark plugs deliver and spark that ignites the gas in the combustion chamber and turns the engine. Spark plugs are exposed to extreme conditions (heat and carbon buildup) that slowly wears them out over time. Most vehicles require spark plug replacement every 60,000 to 100,000 miles to keep them from wearing out completely. When they are worn past the specified limits, the spark can weaken or stop completely, which won’t allow the fuel to be ignited. The symptoms we normally see are misfires and rough running from the engine, along with check engine lights on. Most spark plug problems can be prevented with maintenance tune-ups and replacement at the manufacturer’s recommended intervals, but problems like oil or coolant leaks can cause them to fail sooner.

Dirty or Broken Engine Sensors

Engine sensors like the mass air flow (MAF) sensor are sometime the culprit when you experience engine hesitation issues. These sensors measure the amount of air entering the engine, which is then read by the ECM to adjust ignition timing, fuel delivery, and help the vehicle run smoothly. MAF Sensors are exposed to oil, debris, and heat, which can cause them to fail. When they are unable to read air flow or transmit accurate data to the computer, you will experience sluggish or rough acceleration.

Fuel Pump Problems

The fuel pump moves gasoline from the gas tank to the fuel injectors, but if the fuel pressure is too low or inconsistent, the engine will not have enough fuel to run smoothly. Fuel pumps wear out over time, and can be exposed to more heat wear and tear if your run your fuel tank to empty frequently. When the fuel pump begins to fail, you’ll experience stalling, hesitation, and other symptoms, especially when under load and accelerating.

Throttle Body or Air Intake Problems

The Throttle body controls how much air is allowed into the engine by opening and closing. Most modern vehicles use an electronic throttle body, but older models had cable-driven throttle systems. Whether due to false readings from other sensors or a mechanical problem with the throttle body itself, if it does not function properly, it can restrict air flow to your engine. Engine air filters also restrict the oxygen delivered to the cylinder for combustion, and if it becomes clogged, it can reduce engine power and fuel efficiency.

Transmission Problems

While not directly related to the ignition and combustion of the engine, the last major cause of hesitation when accelerating is transmission problems. Transmissions slipping, missing gears, or being in the wrong gear can lead to symptoms that feel like engine hesitation. Some models are more prone to shuddering, like the Ford Focus. Part of our diagnostic process is to determine whether the symptoms you’re experiencing are coming from the engine itself or the transmission, and get to the root of the problem.

When Should You Have Your Vehicle Inspected if it Hesitates

If your engine is showing any of the symptoms listed above, hesitating when you want to accelerate, it’s important to have it inspected. Each of these problems will continue to get worse over time, and can lead to other, larger repairs on your engine. The first sign you need to get your vehicle inspected is the check engine light, which often comes on before the larger physical symptoms get more pronounced, but sometimes there is little to no warning when the vehicles parts fail.

How to Prevent Acceleration Problems

Routine maintenance based on the manufacturer’s recommended intervals for things like oil changes, filter changes, and spark plug replacement are the easiest way to prevent other rough running issues. Each vehicle has a specific schedule for how often you should replace spark plugs and other parts to keep the engine healthy and running like it should. Our team at Jamie’s Tire & Service has the resources to check when each vehicle should have these services performed, as well as see history of when it was done last. With each oil change, we check other important maintenance items to help keep you informed and up to date on your engine’s needs.

Schedule a Professional Engine Diagnostic

Are you experiencing hesitation when accelerating, misfires, or sluggish engine performance? We can help! Our ASE-certified technicians have diagnostic scanners and tools to help determine EXACTLY what is causing your engine to run poorly. One of the major benefits of thorough engine diagnostic is that you won’t waste time or money replacing parts you don’t need. While it’s easy to start by replacing the spark plugs, we’ve found it’s more time and cost effective to determine what’s wrong with the engine and replace only what is needed to make it run properly again. If you need professional help with a check engine light or rough running problem with your vehicle, call the pros at Jamie’s Tire & Service to get your car or truck running like new again! We’ve been helping drivers with their mechanic and auto repair needs for over 50 years and would be happy to show you why thousands of people trust our team to work on their cars.

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