Knocking when jerk accelerating?

[Guizado]

Hi guys, I own an Ibiza Sport TDI 110 MK3, recently I have noticed a knocking noise if I press the accelerator very quickly (not a full press to the bottom) and then let go immediately, like a jerk push on the pedal and release straight away, its like metal on metal noise and only does it once for like half a second then it stops, if I just press the accelerator to the bottom but don't let go it only does it occasionally.

Any ideas?

Many Thanks

 

[Seatmann]

Engine mount would be my first guess, open the bonnet and watch the engine as you rev and let the clutch up to the biting point, you should see it bouncing if it is a mount.
Another option is where the exhaust goes down behind the front sub frame there's a mount for it and it's common that the mount breaks.

 

[Guizado]

Many Thanks, I think it might be the exhaust because, sometimes when I am stopped on the traffic lights I hear a loud horrible vibrating sound just under the gear box, but if i rev the car up to 1000RPM(the car idles at around 900) and keep there whilst stopped the horrible vibrating noise disappears, and I am almost sure that is from the exhaust I never thought the other knocking sound could be the same.

I will investigate this weekend.

Many Thanks