It uses an RcXel ignition, the plug cap must be pushed down far enough to cover the hex of the spark plug, if it doesn't it is not on all the way, eat some Wheaties and push hard! Once the cap is all the way on you will not need to ground the shielding to the engine at all and your interference will go away providing you have separation from the rest of the flight controlcomponents. The extra wire you see in the picture is not for grounding, it is an accessory lead with a battery plug on one end for connecting power to the RcXel ignition module, it's included with all RcXel ignition systems but almost never used.</p>