Idle speed dropping

[toolsplus]

when on tickover,in drive or reverse,the idle speed drops a bit low and starts to chug.It feels like a possible stall but it doesn't stall.
it's been like this for while now and I'm getting concerned because it's distracting while parking.
any ideas

 

[karl2000]

How many rpm is your usual tick over idle?

You have accidentally got the Power Heater on have you?

 

[toolsplus]

no power heater on
normally ticks over at 650 to 700 revs

 

[toolsplus]

turned the fuel mapper to +15% and normality was restored,it was on 0%. I think the morning temperatures here played a part,being minus deg.C.
was about to spend the day investigating,now I've time to chill