Q: Car not speeding up smoothly, service engine light on when first start driving and car vibrating

asked by on February 15, 2017

Twice over the last three mornings, when my car engine is cold, my car has been vibrating a lot and jerky, especially noticeable when the car is at a stop. The service engine soon light is on when the vibrating is happening. When my car warms up, ~5 min later or so, the vibrating stops and the service engine soon light goes off.

Aside from the vibrating issue, the car has been very jolty when speeding up. This doesn't appear to have any connection to the car warming up / amount of time driving. It doesn't drive smoothly anymore.

My car has 45000 miles.
My car has an automatic transmission.

Hi There, It sounds like you may have a dirty or faulty mass air flow sensor. The problem this can cause may also be compounded when the engine is cold due to the change in air density in cooler weather. The mass air flow sensor monitors air intake as it is mixed with fuel prior to being injected into the motor. This sensor relays information about fuel and air temperature, air speed entering the motor and many other things to the ECM which uses this to make adjustments to fuel supply to the motor. A dirty or faulty sensor can cause an imbalanced air/fuel load to be supplied to the motor which results in an over fueling or under fueling situation depending on the conditions. This type of inconsistent fuel supply to the motor may cause a hesitation, loss of power, a jerking reaction, potentially a bit of black exhaust smoke and typically a strong smell of fuel when this sensor is malfunctioning. I would suggest having a professional from Your Mechanic come to your home to diagnose and inspect your vehicle.

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