i have a 93 rx7 auto which has recently been in my mates paint shop for about a month.when i went to collect it the car it wouldnt start.i messed about with it a found the plugs were not sparking.i replaced the plugs and the car fired up straight away.
now when i drive the car and the revs build up it gives a big back fire out the exhaust and revs die down.
can anyone guide me to what could be causing this problem???????

 

It was probably flooded. If so, it might take a few drives to get everything cleared out.