Hunting at idle ?

Couldnt see a coolant leak on the freelander, but it was loosing it ! K-sealed and the issue has stopped - great

drove it for a week no problems - now though it has started hunting at idle

it runs on lpg, but also does the same on petrol

it has been checked over for any air leaks - nothing

tends to start when sat in traffic, either with clutch dipped or out of gear / handbrake on

holds at 800 odd for a bit, then goes up to 1000, then down to 400, then up again - every time increasing until about 1500 revs

any ideas ???

should add

normally about 44 litres of lpg gets me 240 miles

but since this has started 240 miles was 52 litres of lpg

that said I had changed pressures to 26psi (guy i bought it off had then at 38) between refills - and this was after a motorway run, when car was at 4000 revs most of the way

it sounds air leak, is the throttle body working freely.

thanks for replys,throttle is working fine and i do think an air leak aswell,i will have a look when i get some time to myself!(when the missus lets me)lol