When the choke solinoid is connected the car has a misfire, the engine management light is permanantley on and the tick over kills down to 1500rpm, however when it isn't connected the car runs fine, what could it be?

. Check for codes.

. Clean (or replace) the Idle Air Control Valve (IACV), upper and lower ports, throttle plate, and throttle body. Afterwards, clean the air box and replace the air cleaner.