corsa 1.2 1999 auto 16v engin management light coming on

[norma-milne]

My Corsa 1.2, 1999, auto. 16v has a problem of when driving the engin management light will come on for no reason and will not go out again until you put your foot back on the gas pedal, occasionally while driving normally the car will suddenly pull back then run normally and engin management light comes on again and the rev counter occasionally sticks at around 1200-1500 revs when slowing down to stop and if I put my foot hard on the accelerator and take it straight off it will go back to normal running