I just bought a Fairmont el with the owner putting in a gas tank so that it can be a dual fuel which looked good inside and out and after driving it for a few hundred kilometres the issues started;
1] its started backfiring when starting the car with a loud bang and almost blew up the engine(on gas)
2] the engine switches off when on drive and foot on the brakes when on idle the rpm plays between 0.25-1.75(mostly on petrol)
3] the air conditioner only blows out cold even when the engine is hot as hell (my friend who once own the same type of car says its the thermostat but I doubt it)
4] in the cold the steering wheel is hard to use only then after playing with it, its goes back to normal
5]when you start the car you have to step on the gas for a while before it starts raving (its consumes a lot of petrol and gas)
the previous owner only used gas after putting it in the gas tank and didn\'t use the car for 2 months before I bought it.
so please tell me am I screwed or what?

I am not 110% sure

my EA has a similar problem regarding heater not like we need it , my thermostat is fine , maybe it could be the heater tap seizing up ?

Maybe oxygen sensor not like they do much much but try test with a multimeter should read inbetwen 0.1V to 1V fluctuating every few seconds

has it 'blown' any hoses off in the engine bay? car an x drove would backfire sometimes & pop a hose off - don't remember which 1

as too consuming ya juice ... it 'may be' related to a hose off?? [previous comment]
did said previous owner get a compliance plate for the gas system?
and ... other questions ... dunno

Check the. Map sensor hose has not popped of, it's located on the firewall almost directly behind the throttle body.