[CorsaDan]

I have a Corsa C 1.0, the engine is running very noisily and when Im cruising at 30/40 mph it seems to loose and gain power rapidly. Iv got a warning light for emissions and there seems to be more steam from the exhaust than usual. Iv taken it to 2 garages already and they're saying it could be the timer belt needing replacing, but could that be causing all them problems?

 

[taurus]

It won't be the timing belt because it doesn't have one. The camshafts are driven by a chain on those.

It's impossible to comment on engine noise without hearing it first hand, so you will need to investigate the source - invest in a mechanic's stethoscope, it's an essential tool to have in your kit.

http://www.justoffbase.co.uk/Tool-Shop/Mechanics-Stethoscopes

In terms of the power loss - check for engine fault codes before making any guesses. (At a random guess - a sticking EGR valve often causes problems on light throttle settings, ie when you're cruising at a steady speed. You could try disconnecting it and see if there is any difference.)