Mitsubishi Carisma engine problems

when car engine is running in neutral its ok revs up fine, put it in drive or reverse and start accelerating and exhaust starts popping and revs drop from 4000 to 1000 with pedal flat to floor after 2 seconds it goes back up after 2 seconds goes back down causing a jolting motion at 20mph cannot go faster, popping noises are constant sometimes the car won't accelerate at all and stalls often. same in reverse, the car drove 4 miles and failed to drive altogether just popping and jolting. managed to reverse out of bus stop into sainsbury's car park about 60 metres with trouble and put back in drive, car paced forward suddenly and parked it up. burning smell coming from car. not driveable and also ball joints are rattling a while before this and mot due end of month its an automatic not manual