hat will most likely cause P0509

Question

Replaced Idle Air Control Valve. Car will only start with foot on accelerator/stalls when released

Answer 1

Hi there

This could be an issue with a vacuum leak along the engine someplace. The computer will see that it cannot control the idle and blame the IAC and set the code, however it could be the result of another issue. I would also try cleaning the throttle body ass well.