C5 'hiccup'

[MadMalx]

Was driving my 1.8 petrol C5 today and when slowing to approach a roundabout, saw nothing coming so re-applied the accelerator and heard an odd metallic noise but car responded ok. It wasn't till I glanced in my rear view mirror that I saw the small blue-ish cloud I'd left behind It hasn't done it again, but I'm now concerned as to what it could be? Anyone got any ideas? I've checked for fault codes with my universal reader, but none are showing up

[Peter.N.]

Could have been pinking but I didn't think modern petrol engines could do that.

Peter

[qprdude]

Is your exhaust any noisier?

[MadMalx]

Rear silencer is a little raspy, but don't think any more since this happened.

[qprdude]

Just thinking you might have blown a bit of a silencer baffle out the tail pipe.

[MadMalx]

Maybe, I'm wondering whether this is linked with my ongoing misfire at 1600/1700rpm, which was put down to possibly being a sticky egr valve. It's been cleaned, just not replaced, and the miss doesn't always happen.