UK Focus Zetec 1.6 makes a fluttering noise accelerating in low gears

This happens when the engine is cold and warm. It is a water-like fluttering noise accelerating when in 1st and 2nd gear, especially if the revs are quite low. Is it something to do with the transmission?
My car has just been serviced, has only 15k on the clock and performance doesn't seem to be affected. The noise is relatively quiet but still annoying me. I just want to know what's causing it, should i be worried, and should i have my dealer look at it? Cheers in advance, Jeff
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Sounds like pinking (or pre-ignition to give it its correct name). It's caused by being in too high a gear with the revs too low. I get it on my 1.6 if I change up from 1st to 2nd too early.
Using a higher octane fuel like Optimax or the BP equivalent will also solve the problem but try holding on a bit longer before changing up first to see if its any better.
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Paul Giverin

British Jet Engine Website http://www.britjet.co.uk
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