Q: Violent jerking at stop lights

asked by on December 31, 2016

Long story short my daily beater has been acting up. Have had the car over 5 years always tried to keep up with maintenance and repairs if needed. Starting December I noticed my car sputtering in and out. I drive a lot so I need to properly address the issue before throwing money at it or clunking it . Anyway started small and barely noticeable but now I don't even wanna drive it since it does it a lot at stop lights when I press the brakes and am waiting for the light to turn green feels like she wants to die on me. After doing online research and having some what of mechanic experience I did the following. Battery was 4 years old so got a new one didn't fix the issue. Checked the alternator by turning car on and removing battery to see if car maintained charge and it did. So I opened the car up cleaned the MAF, throttle body , checked the intake systems for leaks (couple hoses needed to be replaced) replaced air filter, checked all sensors and relays and nothing. So here I am:(

My car has 178000 miles.
My car has an automatic transmission.

Hello There, It sounds like you may have a dirty or faulty idle air 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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