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Engine hesitates during acceleration Inspection Service & Cost

It can be frustrating for any driver to expect certain acceleration from their vehicle only to find that the vehicle seems to be hesitant while speeding up. This hesitation could be potentially dangerous in situations like entering and exiting the highway from an off-ramp, where acceleration may be necessary to merge with traffic. A vehicle that struggles or hesitates to accelerate may be unpredictable and moments of hesitation may be coupled with equally dangerous moments of surging or unexpected acceleration. When a vehicle is hesitating during acceleration, it should be inspected by a mechanic.

How this system works:

A vehicle with a combustion (gas or diesel) engine requires an exact mixture of fuel and air to run efficiently. If this mixture is thrown off in any way, it may result in an engine running too lean (not enough air), or too rich (not enough fuel). An engine that is hesitating to accelerate is most likely dealing with a fuel/air mixture that is too lean. Engine’s that are running inefficiently will begin to show signs like hesitation which will only become worse over time. If you notice some symptoms like hesitation, you should have your vehicle inspected immediately.

Common reasons for this to happen:

  • Mass Airflow Sensor: The mass airflow sensor measures how much air is entering the engine and relays this information to the vehicle’s computer so that the right amount of fuel can be delivered from the fuel injectors. When a mass airflow sensor begins to fail, it will typically generate an error code or “Check Engine light.” This warning may be accompanied by hesitation while accelerating, or while driving up a hill. A vehicle with a failing mass airflow sensor may also stall soon after starting.

  • Fuel Pump: The fuel pump in most modern vehicles sits inside the fuel tank and pumps fuel up to the engine. If a fuel pump cannot provide the correct pressure, fuel may have difficulty making it to the engine. A vehicle that hesitates while accelerating or while driving up a hill may have a weak fuel pump.

  • Throttle position sensor: A throttle position sensor tells the vehicle’s computer how far the throttle is open and how hard the accelerator is being pressed. The computer is then able to adjust the fuel/air mixture going to the engine so that is stays at an appropriate level. If the throttle position sensor is not working properly, it may be sending incorrect information to the vehicle’s computer. The computer may then not provide the engine with the correct amount of air while accelerating, causing a hesitation sensation.

  • Dirty/failing fuel injectors: Fuel injectors spray fuel in a fine mist into the cylinder where it is mixed with air and ignited by a spark plug. Fuel injectors may become dirty over time and not be able to provide as much fuel to the cylinder as is needed. Dirty fuel injectors may cause the engine to run lean which will in turn, cause hesitation when accelerating.

What to expect:

A top-rated mobile mechanic will come to your home or office to determine the reason why your vehicle is hesitating while accelerating. The mechanic will then provide a detailed inspection report outlining the nature of the hesitation and the cost of any repairs that need to be made.

How it's done:

A mechanic will first plug into your vehicle’s computer using a code reader/scanner to better identify what the exact issue is. In addition to reading trouble codes, he or she should also be able to get readings of oxygen/fuel intake to make sure those numbers are where they should be. Once the mechanic gets this information they can begin to fix any potential issues.

If the mechanic believes that the mass airflow sensor has gone bad or is failing, he or she will first examine the sensor for any superficial damage. The mechanic will also ensure that the sensor is wired correctly and that no damage has been done to the wire harness. The mechanic should then remove the mass airflow sensor and replace it with a new one if necessary.

If the mechanic believes the problem is the fuel pump, he or she will remove the fuel tank if necessary to inspect the pump. If the pump has indeed failed, the mechanic will replace it. If the fuel tank itself it beginning to show signs of age, it may be convenient to change the pump and tank at the same time.

If the mechanic suspects the throttle position sensor, he or she will test the throttle position sensor and it’s wiring to see if it is functioning properly. If it is not, the mechanic will remove the throttle positioning sensor and the wiring and replace them. In between removing the old sensor and replacing the new one, the mechanic should take the opportunity to clean the throttle body. The mechanic will then ensure the new throttle positioning sensor is working properly and transmitting the correct information to the vehicle’s computer.

If the mechanic believe the problem is dirty or failing fuel injectors, he or she will inspect the injectors to check for any signs of damage or leakage. The mechanic should also take this opportunity to replace the fuel filter if it is not a part of the fuel pump. They will then replace the injectors and test them to make sure they are functioning properly.

In all cases, the mechanic will start the vehicle to make sure that all of the new components are working properly. In the event that an issue has caused a warning light to come on, the mechanic will be able to clear the trouble code associated with the light using a reader/scanner.

How important is this service?

Sluggish acceleration can be annoying for drivers who expect more power form their car, but it can also be dangerous in certain situations. The unpredictable nature of an engine that hesitates can increase the chance of a potential accident especially when trying to merge in and out of heavy traffic. If you notice that your vehicle seems to be underpowered, especially when accelerating, you should not drive it if possible until it can be inspected by a mechanic.

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