Hi guys, I know this topic has been posted about a million times, but I was just looking for a few ideas off people.

I have an EB series 2 fairmont, duel fuel (only running on LPG at this time).
Was running well, with a very occasional small back fire/ miss fire when applying heaving braking and getting back into the accelorator hard again straight after.

The other day I was pulling up home and all of a sudden she couldnt hold an idle, put it in reverse and it stalled. Car turned on after, was ideling rough as hell at about 150-250 rpm gave it a slight rev to stop it from dying and then big backfire.

Car is still running and driving but is now stalling and backfiring quite consisantly now.

It seems to be not too bad when in park or nutural, but as soon as you select a drive gear it gets really rough and the revs drop, you have to keep foot on accel to keep it from stalling.

It only backfires after you brake (revs drop hard because has no accel load) and you accelerate again.

Car runs fine however once you get going. On the road no worries at all, even sitting on 50kms and taking foot off accel it holds its revs fine. Only time it has trouble is when you are sitting on idle, pulling up to lights, intersections etc

Will check vac lines tomorrow, give tb clean
Ill check the plugs (see if its a possible head gasket)

Also are eb and ef map sensors interchangable if so Ill change that over tomorrow aswell.

Could it be the coil, known for backfiring if dodgy especially when lpg car (dont think its this though as it only has trouble with backfiring when its almost about to stall and you give it a rev to stop it/ just take off from slowing at an intersection).

Any ideas? Might just be something little, im not used to the old box cars just yet so any ideas might help

It has to be running lean in those conditions so as you suggest look for vacuum leaks or similar. After that there are two main items affecting idle and air flow - the TPS and the IAC. Since TPS has less input on LPG check your IAC is working correctly. They can benefit from a clean occasionally.