The isolator will make sure any RFI that the servos might be picking up are not transferred back to the receiver, however, it won't block any RFI the receiver's antenna might be picking up. It protects against the possiblity of long servo extensions picking up RFI and routing that back to the receiver so it protects against that scenario but if you have a metal to metal vibration the receiver (not the servos) is picking up or if the receiver itself is picking up RFI from the engine, it won't help. A choke on long servo extensions would probably do close to the same thing.