Both excellent answers by RichardV6 and Deejay
Easy way to check throttle cable function is when this is occurring check the throttle cam quadrant at the throttle body and see if you can manually rotate it further to the shut position. if so then inspect cable and throttle butterfly function.
Throttle body is plastic and if for some reason the mech's have taken yours of to clean the MAF sensor and throttle spindle it is very easy to over tighten the retaining jubilee type clip. This pus a force on to the plastic body and distorts it enough to prevent it closing correctly, air can then pass the butterfly valve and the sensors read this as throttle being applied. Solution. Loosen the clip until fully loose and leave it overnight then tighten very carefully and only just tight enough to hold the clip from moving, it really will not feel as though you have tightened it adequately but any more and distortion can occur.
