I don't know if this could be a accelerator cable or just a gummed up throttle body. Sometimes when I am driving a let off the gas the car will stay at the same speed and rpms as before I let off the pedal. I can also replicate the problem in park by lightly pressing the gas pedal.
I replicated the problem with the car in park and found I was able to lift the accelerator cable arm up and felt a click as the tb fully closed.
Any suggestions??
Couple weeks ago i sprayed carb cleaner into the throttle body with it still on the car. It was fixed for a few hours.
Its a 97z, a4.
Also I don't know if this could be part of the problem but I have a code PO420 Bank 1, which is going to be warranty work by the dealer.
Thanks
Brian

 

I had something just like what you describe happen on a chevy truck. Turned ou to be the TPS. Just my 2 pennies

 

Maybe the cable needs to be lubricated

 

I've tried lubricating the cable and it didn't help at all.

 

After I cleaned my TB, my RPMs would hang. I dipped a QTip in oil and dabbed it on the butterfly shaft where the shaft enters the body. Problem solved.