My car recently developed a surging idle and my dfi is retarding timing @6* to steady the idle. I pulled the cap (Carquest brand, brass terminals with @ maybe 5 hours of run time) and it was very corroded. I ordered a new msd cap n rotor and cleaned up the reluctor ring (slight surface rust, I bought it used with @100 miles on it) but the problem is still there. All the wires, plugs(.040) and coil are new. How do I check the magnetic pickup (which terminals) with an ohm meter? thanks