Engine surge in revs when throttle lifted

[Z3I]

Can anyone point me in the right direction please!

When I lift off the throttle when changing gears, or even when standing still, and I blip the throttle, the revs surge for a second, and then die. Is this a known problem?

Car is a 1998 2.8

Thanks!

 

[Ianmc]

Is the floor mat in the right place? Cable sticking?

 

[Z3I]

Actually had the mat, and the plastic under dash fitting out just to check, but no, not that.