Domestic Vehicles are known to have really poor electronics, wires, and connectors. You need to make sure your number one running directly to the battery. Two make sure you are not routing any of your power or coax near any of the wiring going tot he ECM/PCM! Third, you need to ground the engine really well! Fourth use LMR240, 400 or the like! Finally, make sure you do not have common mode current on the coax radiating into the vehicle! P.S. My family has owned mostly Toyota's since 1979 and never a problem but all the GM, Ford and Chryslers always had electrical problems often under warranty and always once outside of warranty.