so on my previous thread I posted that I was get check engine code p040, which is Catalyst System Efficiency Below Threshold (Bank 1), and some other codes along with it of course,, it's Audi. Any ways I was told that its probly not the muffler but the O2 sensors.

recently every time I step on the gas and go slow, I can hear loud cranking noises coming from the driver's side. Once I start going fast though, the sound disappears. Also if the car is completely stopped (have it on P, or N), and I step on the gas, there is no noise. So the noise only comes up when I'm just starting to move, but the noise is really noticeable.

Please tell me if this sounds familiar, and if I should stop driving the car till I get it fixed. I'm away from home so I can't fix it now, but I guess I can park it for a while.