Hello,

My 99 Grand Marquis has an issue, usually 5-10 minutes after starting when the vehicle will make a humming noise. It can happen while driving or while stopped at a red light. While driving, I usually tap the accelerator a few times and it goes away. While at a red light, the humming stays and the car wants to lurch forward, if I don't have my foot on the brake, the car moves forward a lot faster than usual as if I was lightly pressing the accelerator. The car will jerk back in place after the humming stops. The only code the car is throwing has to do with the catalytic converter. I am not sure if they are related.