Q: Why does my Echo rough idles at a red light or stop sign?

asked by on January 19, 2017

Every single time I shift my car into drive with my foot on brake, the car rough idles until I hit the gas. But every time I stop the car, it rough idles again.

The Echo is a VERY smooth drive on the road, it just sucks when I stop at a red light. Engine filter is new. Throttle body and plate has been cleaned. Spark plugs changed out last year. I am lost on what to do.

My car has 172600 miles.
My car has an automatic transmission.

Hello, What you are describing is a common sign of a dirty or faulty idle control valve. The idle air control valve is a small valve on the engine’s intake system that reads the air intake as it comes into the motor. This is controlled by the car’s ECM which uses this information to make adjustments to the air/fuel ratio depending on various inputs such as outside air temperature, intake air temperature, load and various other things. As you accelerate, your car’s engine is receiving a much higher dose of fuel than when at idle and conversely, when you let off the gas pedal, there is a sudden change in this fuel supply as a result of your foot letting off the pedal. When this happens, the job of the idle air control valve is to bring this deceleration down to a slow and smooth idle rather than suddenly cutting off the fuel supply causing the motor to die. When the idle air control valve is not working properly, this cause a disruption in this process resulting in the engine not being able to idle properly. I would recommend having a professional come to your location to diagnose and inspect your vehicle.

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