Noisy rattle on cold start

[jp928]

today, for the first time, out of warranty, I get a very noisy rattle up the front on cold start. Stopped quickly, have a look, nothing visible amiss. Try again, same. Remove engine cover, get a light organised , start it up - noise gone.
I seem to recall seeing something similar here recently - recall something about air injection pump coming on cold start to dilute nitrogen oxides or ??

Suggestions please?
Might try looking at the diagnostic read out, but might have too many starts on it since, and I think they clear if not repeated in maybe 5 starts ?

jp 08 gtb 6mt wagon

[jay.ritchie]

Keep an eye on it. (or an ear).
Although different, mine had a rattle on idle, it was intermittent and it turned out to be a failing timing chain tensioner.
Probably best to get it checked out if it gets any worse just to be safe!

[jp928]

2.5T has a belt, not a chain like 3.0, but point taken. I think the belts have a spring type tension controller, but they may have some sort failure mode...

UPDATE: no trouble codes listed. Will keep ear out for recurring, and quickly check trouble codes.
tks
jp 08 gtb 6mt wagon