I have a 2003 MG Rover Streetwise, I need to remove or at least completely bypass the OEM Immobiliser. Driver door lock is broken due to attempted theft, so no point trying to enter the code, the key fob has been destroyed due to an auto electrician's incompetence. I have managed to get ignition, spark and fuel, the car now starts, but will only idle for roughly 30 seconds and cuts out again. No loss on fuel pressure, coil doesn't show loss either and the fuel cut in the engine compartment is completely pressed. I need this car running urgently!
On most cars, the immobiliser is difficult to remove/disable, as it is integrated into other systems on the car. For example, on my 2000 Opel, the immobiliser is linked to the ECU, which means the ECU would need reprogramming to remove.
I would suggest going to the dealership, and bringing proof of ownership. They can then order in a new key and lock set for you. They can look up what key and lock you actually need from the VIN and number plate.
This will probably be expensive, but it will be the easiest option, which will cause the least damage.
The new key will also need programming, which generally needs to be done by the dealership computer software.
EDIT: Seems that MG went bust a while ago... You could try contacting the MG owners club
The immobiliser can be disabled on 90% of vehicles by specialist auto electrical companies. The car will start and operate completely as normal just without the chip in the key.
I don't think there is a major problem with security as most thieves won't attempt to steal a car which they would assume has an immobiliser and there is still the door locks and the steering lock which is very hard to remove.
I know this because I was previously in the same situation and used tgautomotives.co.uk based in the UK. The website lets them down but he explained everything to me and disabled my immobiliser with no issues.
(Im not affiliated with the above company just a very happy customer who wants to help!)