Check out my ignition grounding post below yours. It was me that was flying my RCS 140 with a FM(non pcm) receiver and had a broken ground connection at the point where the plug wire enters the ignition module circuit board. Those two teeny little loops of wire soldered around the HV shield, and circuit board ground plain, are the only ground source for the HV shield, plug cap, and the engine itself. My JR did good I kept getting little hits, but nothing bad happened. This all happened after only one tank of fuel run on the ground, I was flying on the second tank, the engine was running very good. If that ground connection opens up, you will get sparking at the plugs gap(like you should), plus the broken ground connection will be sparking to complete the ignition circuit return to ground. Only because its high voltage does this work. Unbelievably, the engine continues to run like there is no problem. I fear that if I had been using a PCM receiver, the problem would have gone unnoticed untill failsafe kicked in

I fixed mine by resoldering heavier loops of wire around the HV shield wire on the circuit board, and also added another separate ground wire from the circuit board ground plain, to the black wire that is grounded to the shield at the plug cap(the wire you are also suppose to ground to the engine frame). So I now have a backup ground, in case one fails. You should also make sure the plug cap fits on the spark plug firmly. If its loose, it could also be a noise source. RCS suggests a hose clamp around the cap, to hold it on the plug tightly. Another suspect point could be the crimp on pins that connect the ignition to the battery, they sould be soldered. I also added a strain relief to the HV plug wire befor it enters the ignition module.

Another interesting thing, is that I was getting a on the ground range check of around 200 feet, with the antenna down, and engine running. Only in the air did I get the interfierence. Apparently the ground(as we walk on) was absorbing the noise because of its close proximity to the source.

Now that I found the problem, my FM(non PCM) radio link is working flawlessly with this engine.

By the way, there is no resistor plug available in this size.

Hope all of this makes some sence.

Kevin