Volvo: Volvo cuts off when gas is pressed slightly, throttle switch, car idles

Question
I have a 1990 vovlo 740.  The car idles fine, but when you try to accelerate slowly from a stop the car cuts off.  My wife and I have figured out that if we punch the accelerator instead of pushing it slightly, the car will not cut off; not always a pretty sight.  The car drives fine on the highway it is just when you stop and try to accelerate slowly.  Thanks for any advice.

Answer
with the car not running have someone press accelerator while you are under hood with your ear close to back of engine near throttle body (has cables and pulley) there should be a clicking sound when throttle opens and closes , there is a small black plastic box (your car should have one) its a half inch thick, it tells the computer when gas pedal is pressed, if there is no clicking sound thats it. if you want to do it yourself here is the procedure 1) slacken retaining screws 2)turn switch clockwise slightly 3)turn switch back again until click is heard 4) tighten retaining screws, you will need a 3 mm allen wrench, (sears has it), the part is called throttle switch