5 Causes of Engine Hesitation at Idle, When Cold and Under Load

Last Updated on June 3, 2019 by themechanic

The internal combustion engine is constantly generating power so that the wheels underneath the vehicle can rotate. When you step on the gas pedal to go faster, the engine works faster to generate more power for this faster movement to occur. But if there is ever any engine hesitation, then your engine won’t be able to generate the power needed to satisfy the demands that you’re putting on it.

Engine hesitation doesn’t just happen when you’re driving, though. In fact, engine hesitation can happen at any time the engine is running. It could happen when your vehicle is sitting idly in traffic, experiencing cold temperatures or hauling a heavy load. This would actually be better than if it were to happen while you’re moving because inconsistent engine performance is a safety risk if you’re moving too fast.

On the other hand, engine hesitation can still damage your engine, which would be a horrible scenario for your wallet. It would cost you thousands of dollars to replace your engine if it were damaged bad enough You might as well purchase a new vehicle if this were to happen.

5 Common Causes

The best way to prevent your engine from getting damaged is to fix whatever is causing the engine hesitation problem. In many cases, it will be a minor component that you need to replace for a reasonable price. This is much more affordable than having to pay to replace your engine. Just be sure to figure out the cause as quickly as possible.

To help you out, below are the top 5 causes of engine hesitation when it is idle, cold and under load.

1) Bad Fuel Pump

Newer model vehicles have fuel tanks which have their fuel pumps built directly into them. As you know, a fuel pump creates the pressure needed to move fuel into the cylinders of the engine for combustion. The pump needs to deliver the proper amount of fuel or else there won’t be successful combustion. If the pump is bad because it’s worn out or damaged, then it cannot generate the proper pressure to move the fuel. That is one way that engine hesitation can happen.

2) Bad Mass Airflow Sensor

The mass airflow sensor calculates the amount of air flowing to the internal combustion engine, where it is mixed with fuel before ignition. The engine control unit reads this information and tells the fuel injectors to inject a specific amount of fuel, based on the data received. But this cannot happen successfully if the mass airflow sensor is bad because it will send the wrong information to the unit. Then it will cause the wrong amount of fuel to get injected.

3) Clogged Fuel Filters

Before fuel enters the engine, it passes through a fuel filter which cleans out any dirt, dust, particles or other debris that may be in the fuel. As time goes on, this debris builds up on the fuel filter. If the debris builds up too much, it will prevent fuel from passing through the filter and enter the engine.  That will cause engine hesitation for sure.

4) Bad Fuel Injectors

The fuel injectors themselves do not last forever. They can get damaged or turn faulty too. This will cause them to deliver the wrong amount of fuel to the engine cylinders. This, of course, will cause engine hesitation when the engine is put under a lot of stress or sitting idle.

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5) Bad Throttle Position Sensor

The throttle position sensor detects the openness of the throttle and the amount of foot pressure you put on the gas pedal. It sends this information to the engine control unit. From there, the unit will allow the right amount of fuel and air to mix together to satisfy the demand you’re putting on the engine, based on how hard you’re stepping on the pedal.

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