Electronic Ignition Help

Do you have any resistance device such as an electric choke spliced into the run side if ignition circuit? If so this will cause low voltage at +coil terminal, and poor idle quality. One way to check if you have an electric choke, is to unplug the + wire feeding the choke while engine is idling; if idle quality improves, you have found some of your problem. If this is the case, we have an easy solution to that situation.

An improper ballast resistor can also over reduce voltage to +coil terminal which will kill idle quality. Voltage on high side of ballast has to be a minimum of 13.5V, and coil side of ballast around 5-6 volts with stock coil. Less than five volts at coil, and the car won’t idle very well. As you have discovered, start circuit delivers full battery voltage to coil just long enough to get the engine started, than when key moves back to run, the coil receives 5-6 volts.

As 67Dart273 said, you need to test for voltage drop in the ignition circuit. 0.10 to 0.20 volts is tolerable, any more voltage reduction due to poor connections, bad wire, worn switches, or whatever will cause drivability and charging problems. Another place to look for voltage drop is in battery terminal connections, ground strap connections, and grounding of voltage regulator’s base, spark control’s base and alternator. A voltage drop in ground side of ignition circuit also adds up to cause problems as well. You may have make up a ground loop by running a #14 wire from negative battery terminal to base of voltage regulator, spark control base, and alternator to bring any zero out any ground side voltage drop.