idle problem

my '94 grand am when the car is at idle the service light comes on, some time when I start driving the light bgoes out other I have to turn off and on the engine the light goes out till I stop again.

I have replaced the idle air control valve still the same problem.

thank's

Have the car scanned while the light is on and it should give you an indication of what is going on. Autozone will do it for free. Once you get the code, post again and we should be able to help diagnose the problem. Autozone can also help you repair the problem. One last thing, make sure the gas cap is tight. Sometimes that can cause an intermittant light.