Why does a car backfire?

[george allen]

I always thought it was the timing. But with modern electronic ignition systems should it still happen? My daughters year old fiesta backfired a couple of times when standing at the lights. She managed to pull away ok then it started running ok.

[mr rusty]

it is still possible with a modern car- mixture problems caused by leaking manifold gaskets can cause it.....the effect is normally most noticeable on the overrun though, rather than standing idling. There could also be a sensor problem somewhere or a glitch in the software.

Presumeably it's still under warranty, so book it in to get it sorted- maybe the diagnostics will show something up.