Q: When i start car in the morning, it vibrates with a rattling noise under

Hey there. This sounds like you may have a rough idling problem that tends to get worse once the car is put into gear. This can happen for a variety of reasons such as low fuel pressure, faulty fuel injectors or a dirty or failing idle air control valve.

Low fuel pressure will cause the fuel injection system to provide less than the required amount of fuel needed for the car to run smoothly. This may also be true when you have dirty or malfunctioning fuel injectors.

The idle air control valve monitors the air intake as it is mixed with fuel prior to being injected into the engine at low speeds and at idle. This valve is controlled by the vehicle’s computer which will adjust idle speed based upon other measurements such as engine temperature, intake air temperature and electrical system load or voltage. When you accelerate, the engine RPM increases, and as you let off the gas, the RPM slowly returns to the normal idling speed with the help of the idle air control valve.

If you would like to have this all checked, I recommend having a certified technician from YourMechanic can come to your home or office to diagnose the vibration issue and advise you on needed repairs.