Thinking of fitting an induction kit I have to my fiesta until I get a J1 but the one I have at the moment doesn't have a connector for the sensor, will leaving the sensor unplugged be bad for the engine?

Thinking of fitting an induction kit I have to my fiesta until I get a J1 but the one I have at the moment doesn't have a connector for the sensor, will leaving the sensor unplugged be bad for the engine?

Yes, the MAF (Manifold Absolute Flow) sensor reads the airflow into the engine for the ECU (engine control unit) the ECU adjusts the air fuel ratio from this, if it is disconnected the air-fuel will be wrong, potentially causing poor performance/ economy, MOT ennision failures and/or contaminating the catalytic converter - some engines will go into "limp home mode" with it disconnected,

If the filter draws warm/hot air from under the bonnet, it is also liable to loose power- thats why they make cool air intake/s systems (CAI/S) cooler air into the inlet = denser air = more oxegen for given volume = more power/ torque (the reason intercoolers increase power on turbo engines)

You could make your own mount for the MAF,(eg - drilling a section of alloy tube etc) or cut off the part of the stock filter that the MAF mounts onto, (it helps if you are good at these sorts of things)

Ok that's brilliant cheers for the response