Car Hesitates When Driving: 6 Common Reasons and Easy Fixes

Why Car Hesitates When Driving?

Your car will hesitate when driving because of insufficient power. Below are what causes the power issues:

1. Ignition System Issues

Your car’s ignition system ignites the air-fuel mixture in the engine. This helps propel your vehicle on the road. If one of its components becomes faulty, your car can hesitate when driving.

These components include spark plugs, an ignition coil, spark plug wires, and a distributor. The hesitation occurs when the faulty component cannot ignite the air-fuel mixture.

Diagnosing and Fixing the Problem

You can diagnose ignition system problems by visually inspecting the spark plugs and spark plug wires for any signs of damage. If there is no clear damage, you can use a multimeter to check the resistance of the wires, ignition coils, and distributor.

If there is no resistance, you must replace the faulty components. Here is how to do it:

• Step 1: Disconnect the battery, the negative terminal first, followed by the positive one.
• Step 2: Pull out each spark plug wire from the distributor.
• Step 3: Remove the faulty spark plugs using a socket from the cylinder head. If the ignition coils are bad, remove them too.
• Step 4: Install the new spark plugs, spark plug wires, and ignition coils.
• Step 5: Replace the distributor cap if necessary and reconnect the battery.

2. Sensors Malfunctions

Various sensors, including the Mass airflow (MAF), throttle position sensor (TPS), and oxygen sensor, can malfunction over time. When these sensors malfunction, they usually provide the ECM with incorrect data regarding the amount of air entering the engine.

When this happens, the ECM cannot adjust the air-to-fuel ratio accordingly, causing a lean mixture and hesitation problems.

Diagnosing and Fixing the Problem

One sign of a faulty MAF and oxygen sensor is black exhaust due to excess fuel, accompanied by a check engine light. With a bad TPS, you may notice intermittent flashing of the check engine light.

The solution to this problem is to replace the faulty sensor. Check out how to do it:

• Step 1: Detach your car battery.
• Step 2: Locate the MAF sensor between the throttle body and air filter housing in the air intake tube.
• Step 3: Unhook the electrical connector from the sensor.
• Step 4: Remove the bolts and mounting clips securing the sensor to its housing.
• Step 5: Lift out the old sensor and install a new one in the reverse sequence.
• Step 6: If the MAF has no issues, then locate the throttle position sensor attached to the throttle body.
• Step 7: Disconnect the electrical connector to the sensor.
• Step 8: Remove the TPS from the throttle body by detaching the fasteners and holding it in place.
• Step 9: Install the new TPS and reconnect the electrical connector.

If the oxygen sensor is malfunctioning, here is how to replace it:

• Step 1: Turn off your car and let it cool down.
• Step 2: Jack up your car.
• Step 3: Locate the sensor underneath the car or hood. Almost all modern cars have two. One near the engine and another near the catalytic converters.
• Step 4: Unplug the electrical connection to the sensor.
• Step 5: Remove the new sensor using a wrench and install the new one in reverse order.

3. Vacuum Leak

Vehicles rely on vacuum pressure for optimal power and engine performance. So, when your car has a vacuum leak, this forces more air and less fuel into the engine. As a result, the engine usually hesitates due to being fuel-starved.

Diagnosing and Fixing the Problem

To diagnose a vacuum leak, start the engine. Then, spray each connection along the vacuum lines with a light stream of water. If the water is sucked in, you’ve found the leak.

However, fixing a vacuum leak depends on the specific source of the leak. Below are several possible solutions:

• Tighten any loose hose connections using clamps
• Replace any damaged connection or hose
• Install a new intake manifold gasket if the old one is leaking
• Replace the throttle body gasket
• Repair or replace brake booster

4. Bad or Clogged Air Filter

When the air filter becomes dirty and clogged, it limits the amount of air going into the engine. As a result, this affects the fuel-air mixture, causing the engine to hesitate when driving.

Diagnosing and Fixing the Problem

Typically, a dirty air filter will appear brown or gray in color and have dirt trapped between it.

To fix this problem, you can either clean or replace the filter. Here is how to go about it:

• Step 1: Remove the air filter from its housing, located under the hood near the top of the engine bay.
• Step 2: Vacuum the filter to remove dust and debris.
• Step 3: Wash the filter with soapy water and let it air dry before reinstalling it:
• Step 4: If the filter is old and damaged, install a new one.

5. Fuel Delivery Problems

When the engine does not receive enough fuel due to delivery problems, it can hesitate when driving. This can happen due to a clogged fuel filter, faulty fuel injectors, or a failing fuel pump.

Diagnosing and Fixing the Problem

You can use a fuel pressure gauge to check the pressure in the fuel lines. If the reading is zero, the pump is dead. To diagnose a dirty fuel filter, check for dark discoloration and visible sediment or debris trapped in the media.

On the other hand, you can use a mechanic’s stethoscope or a long screwdriver to diagnose faulty injectors. If you don’t hear a clicking sound, the injectors are dead. 

To fix fuel delivery issues, you simply replace the faulty components. Below are the steps to follow:

• Step 1: Relieve the pressure in the fuel system.
• Step 2: Lift your vehicle and remove the fuel tank.
• Step 3: Disconnect the fuel lines and wiring harness from the fuel pump and filter.
• Step 4: Lift out the failing fuel pump. Then, remove the fuel filter from its mounting bracket.
• Step 5: Install the new fuel pump and filter in reverse sequence.

In the case of bad fuel injectors, you should hire a professional. The job can be tough and dangerous for most DIYers. Below is a video of how the replacement is done:

6. Issues with the Transmission

If your car is equipped with an automatic transmission, issues with the transmission can cause it to hesitate when driving. This is because the transmission plays an essential role in delivering power from the engine to the wheels. Consequently, this allows the car to move at a certain speed.

Such issues can range from damaged clutches to a failing clutch solenoid, worn-out transmission oil pump, and gears slipping.

Diagnosing and Fixing the Problem

You can diagnose transmission problems by checking for any diagnostic trouble codes using an OBD-II scanner. Also, you can listen for unusual noises like grinding, clunking, or whining coming from the transmission.

To fix the transmission issues, here are some possible solutions:

• Check the transmission fluid level and top it up
• Replace the transmission fluid if it’s dirty and contaminated
• Replace the shift solenoids if damaged
• Install a new transmission pump
• Replace the clutch plates if worn out