944 s2 idle - help please

[chris312]

Sometimes after starting, engine runs very oddly - revs dropping very low, then back to normal 900/1000rpm, gradually getting worse until it stalls. A bit annoyimg when pulling up to lights etc. Anyone got any ideas or had the same problem?

I'm guessing a fuel or air supply problem.
As it only happens every 4th or 5th time of firing up, it's a difficult one to get my head round. It does eventually go away if i manage to keep it running, but can't pinpoint it to anything in particular that i do (e.g. a good hearty blast doesn't make any difference).

Any suggestions to rectify, or previous experience of this would be appreciated