Car Jerks When Accelerating

Car jerks when accelerating especially during cold rainy morning when the engine is cold. Several reasons are causing it depending on the condition of the car when it happened. image
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Possible reasons why car jerks when accelerating

Moisture in Distribution Cap 
Since the acceleration problem happens when the engine is cold especially during wet morning this suggests moisture in the distributor cap. This happens because when you park the car overnight especially on the outside, moisture is formed inside the distributor cap because of the wet weather. The moisture allow the electrical current to arc inside the distributor cap that causes engine misfiring because of uneven power is produced and when the engine misfire the car jerks when accelerating.

How to avoid the car to jerks when accelerating because of moisture in the distributor cap. To avoid having moisture in the distributor cap from happening park your car inside the garage if you expect a rain to from coming.

Vacuum Leak 
If the car jerks gradually happened when accelerating and become worst overtime. When the car jerking happens gradually and become worst overtime then this indicates a possible problem of a vacuum leak. When the car has problem with vacuum leak it will not be noticeable initially and it will become noticeable when it get worst. The fuel system creates vacuum in which is one of the key factor in determining the amount fuel the engine will get. When there is a vacuum leak on the system the amount of fuel the engine get will become wrong and this will result in car jerking.

Bring the car to the car shop and ask the mechanic to check for any vacuum leak on the system. Usually the most common parts that are always the source of a vacuum leak is the Exhaust Gas Re-circulation (EGR) and the PCV valves which you should suggest to the mechanic to check.
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PCV Valve image credit
Faulty Throttle Position Sensor 
If the car jerks happened constantly when accelerating at any engine temperature When your car has fuel injection system usually the reason for this problem is a bad throttle position sensor. Throttle position sensor is device present in a fuel injection system, the purpose of this device is to measure how far the driver depressed the gas pedal and feed the data to the car computer which calculates how much fuel the system should inject into the engine. Now, when the throttle position sensor is bad wrong data will be sent to the computer and the amount of fuel injected to the engine will also become wrong that is why the car jerks during acceleration.

Bring the car to a shop and ask the mechanic to check the throttle position sensor. Explain to the mechanic the symptom of the problems you have notice for better understanding of the problem and made the troubleshooting easy.  

See also: Car Stalling While Accelerating


  1. volvo 940 mod. 1993 230 FD. jerking during accelration when engine is cold. starts and run fine idle cold lamba light comes on, but no fault codes it shows 1-1-1. change fuel sensor for temp, lambda sensor almost new and now fault when tested. runned check with valve test throught obd, and valves inj etc works fine. the promolem seems to increase over time hence cold engine acceleraton is almost impossible because of jerking. when warm engine perform perfect
    What can be wrong????


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