Car Idlle - either too high or too low

[dgriff]

Hi

Whatever regulates the idle speed in my peugeot is not working properly. Sometimes the idle speed is too low. For example when I stop for petrol. I start the car up again and it immediately stalls unless I give it a bit of gas to keep the rpm's up.

And sometimes it's just fine.

And sometimes the rpm's are very high in idle. Around 1500 rpm. When it's like this when I'm changing gears (from 2nd to 3rd for example) I put the foot on the clutch and instead of the rpms immediately dropping, the rpms rev up by about another 1000 rpms. Then it takes another second or 2 for the rpms to start falling but not back to a normal level (too high). And when it's in gear I can take my foot off the accelerator and the car feels like it's in cruise control.... I dont have cruise control!

It;s been like this since last week since I was driving in very bad floods we had over here in Dublin. Not sure if that has anything to do with it....

Any ideas? Could it be a fuel mix sensor? If there's any such thing...!