How can i fix my 99 renault megane 1.4 fuel problem?

For the past couple of months every now and then the revs jump around 4500 rpm and feels like some sort of blockage, it only occurs on load and when you accelerate fast but this doenst happen all the time. today i had a similar problem but the exhaust gas warning light flashed and later on the engine cut out completely which stopped the powersteering and eventualy the brakes to work when this happened the oil warning light came on but my oil level is fine. i pulled over and started the car again and it was fine. i realy have no idea what the problem is would be gratefull for any help?? cheers