How to reset electronic control unit (ECU) for vauxhall vectra 1999-2000 year (V reg)?

My Vectra is 1795 cc petrol engine.The problem is.When I'm driving and take off my foot from gas pedal to change a gear by pressing clutch,the r.p.m does not drop down and I have to press gas again to drop running engine down.It's not always happen but sometimes.Another issue is.When engine running on low r.p.m about 800,such I'm stopped on street lights or waiting for something and do not turn off engine the motor try to stop and after come back,so r.p.m goes up and down and again and again.It's also not always but sometimes.Someone told me to reset ECU


Thank you|||First, try turning the key on and off 21 times with a 5 second pause.





If that doesn't work, disconnect the battery overnight. (A residual charge remains so it needs to be more than just a few hours.) Remember to have your radio and alarm codes ready for afterwards.





If that doesn't work you probably need a new sensor, you'll have to get a garage to connect the device that tells them which sensor, or even a new ECU. Sensors are cheap, the ECU is expensive.