I know this has been posted before but everyones conditions seem to be different.

2000 AU FAIRMONT:

Idles completely fine at around 800rpm on Petrol.

When i switch over to gas while stopped i have to give it a bit of foot otherwise it cuts out (i know this is rather normal) but now gas idles around 500rpm and the entire car shakes around rather violently.

I tried adjusting the idle on the throttle but when i tune it so that gas is idling around 800rpm, all of a sudden petrol idles at about 1800rpm... im wandering if there is an idle adjustment JUST for gas somewhere, also when i put my hands over my air filter the idle is fine suggesting its getting too much air?

I dunno but would love some help

Thanks

Factory gas???. If so to idles circuit has some crap in it and needs to be cleaned out. So this means a LPG service if you don't believe you can do it.There's a solenoid on top of the converter.

Nah its not factory gas, and has only been doing this since i pulled it out of the garage after it had been sitting there for a while coz i lost my licence...