ive searched the net for this and come up with a lot of things... i'll start with what happens !

about 3 weeks ago, the wife ran out of gas and wouldnt run on petrol because...the pump relay under the expansion bottle was rooted.. so, towed home, replaced relay , all good on petrol !

took for gas next day to fill it and its basically been backfiring on and off since.. hadnt done it much with me but wife near s**t herself coming home from work as it done it with her first !

seems to be when given more throttle and then it will backfire then do it a couple of times till you let it settle and all good for god knows how long.. sometimes even goes a full tank without a hiccup then bangs three times in the space of 500m !

now, there is a screw (kind of like a idle screw) on top of the mixer thing (not gas savvy ).. and i remeber my mate tinkering with that at the side of the road when it was out of petrol those 3 weeks or so ago, would this affect it ? as i have read backfires are the product of lean mixture ? so i wound it open as it was kinda 1/2 way so one full turn to full open !(tried shutting it off but engine cut out) so i assume thats a misture screw as it idles better now !...... now, i havent drove it since as this was just today.. but, the inlet flexi rubber to airbox is blwn to s**t and now needs replaced but reluctant to do this until backfire has ceased as it could be a costly exercise replacing them lol....

car is 94 EF WAGON, system is 9yr old but freshly tested as i only bought the car a few months ago . had backfire history (taped up hose but not recent).....so may be related to mates actions or coincidence ?

so my questions after this longwinded story is this....

does lean = backfire ?
opening that screw up = more gas= no backfire ?
what are the basic causes that could be the problem ?
what other area's should i be looking at ?

thanks for any help !

yes that screw is the idle mixture screw.
start the car and turn it in till the cars starts to run slower, then turn the screw out till it runs smoothly. probably about 2 turns. u will hear it start to miss if u turn it out too far.

that will give it enough gas to get by, or at least get u to a lpg guy, probably best to get it tuned at a gas specialist

ok, so its pretty much what i thought ! my mate leaned it out by pissing about with it and now backfiring ..so, is it a matter of an exhaust probe or wide band lambda to tune it/set the AFR ?

ok, set it higher last night, ran it for 20mins drive, flogged it and no back fire at all....but..........was a bastard to start... need to get it looked at !

it might be a bit rich still

probably, most engines run better/start better lean ! will still need to get it set, wonder how much that will set me back as i dotn have much work at the moment !

ok, need advice on this if someone can shed any light on it ! i decided to check this valve on the rocker cover near the front (pcv i think??) with two air hoses coming from it. one larger one smaller smaller diameter.. if i pull it((PCV) out of the rocker it stumbles more but if i block the end of it it cleams up a bit. the smaller pipe is blocked off completely with a bolt pushed in but it has run perfect so i am sure this bolt has nothing to do with the issue at hand (s**t idle).
there's another thing, i unplugged the map sensor and the idle rose to about 1100 rpm but was smooth and clean like it was before the backfiring incident but when connected it stumbles and misses...

so,
A, could the backfiring have damaged the MAP SENSOR ?(i assume so ?)
B, why would the small vacuum hose coming from the pcv be blocked off ?
c, where to buy these parts and expected prices..

thanks !