How do I tell which of my spark plugs/plug wires is bad?
If those are the factory wires, they should last the lifetime of your car. For testing purposes, POWER WASH your engine with GUNK orange at a DIY car wash AT DUSK with engine running. A bad wire will light up and sparks will dance around. If you were unlucky enough to have replaced the factory wires with cheap after market ones, that's another issue. On the top of your intake manifold there is a gizmo called an IDLE AIR CONTROL VALVE. If you have been using wax based oils in your engine, this critter will be ALL fouled up. A good cleaning here is in order. Ford designed this engine so that the IAC valve is easily renmoved for cleaning. This thing affects low engine speed mileage and starting. CLean it out with SeaFoama nd Gum-out, and the THROTTLE BODY and PCV, too. Run both chemicals through the intake system to clean off the muck on your piston tops. rings, and valve heads. Switch to Mobil 0W30 engine oil. Change your spark plugs if you are NOT using platinum or iridium plugs. The Bosch and Denso plugs designs work the best. Eiother Fusion or Denso Iridium or Twin Tip plugs will gev you extra power and ileage. GOOD LUCK!!