Q: When cold, Engine shakes and hesitates during acceleration

asked by on January 03, 2017

After the vehicle sits overnight (cold engine), during idle, engine vibrates and after about a minute vibration's gone and comes back again a minute after - this cycle goes on and only stops when the engine becomes hot.

When driving cold, i notice that the engine does not have enough power as before. It hesitates and shakes when going uphill. The hesitation and lack of power problem is gone once the engine becomes hot. But even when its hot i can still say engine is running rough as compared to before.

My car has 150000 miles.
My car has a manual transmission.

Hello There, As a general rule, car engines do not like cold weather and do not do operate as well in cold weather. When you start your car in the morning and turn the key to on, the coolant temperature sensor immediately reads the temperature of the coolant and relays this to the computer indicating that the coolant is cold. The computer then knows at this point that it needs to enrich (add more fuel) the air/fuel mixture at startup due to the change in air density. When you start the car, you will notice that it idles high for a period of time until the engine warms up. This is the enrichment cold start process. This is done with what is called a cold start injector which injects more fuel into the motor until the engine reaches a specific operating temperature. The computer simply feeds a little extra gas through the fuel injectors to start the engine and then maintains a certain amount of fuel supply to the motor until it is warm. I would recommend having an expert from YourMechanic come to your location to take a look at your vehicle and diagnose your cold start issue.

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