Hi folks! Beautiful Fall day here in the Poconos! Simple question . . . what’s the standard test for a failing ignition coil? My old Accord ('89-5sp/460,000 miles/4 cyl with a carb). Symptoms . . . idiot light (battery) once in a while . . . new battery last May . . . flutter in idle and tachometer once in a while. I checked spark . . . at the plug it’s orange, not blue. Any quick checks? This IS the original coil, BTW. Rocketman
I would do two things - check the charging voltage at the battery terminals. Should be 13.5-14 volts at fast idle, and greater than 12.8 volts at idle. These are not specs for your car, just general rule of thumb voltage ranges. If charging voltage is low, clean the terminals from the back of the alternator to the battery. If that does not help, try a new voltage regulator.
The orange spark may be due to low system voltage, so get the voltage up first.
Before replacing the coil, I would clean all the terminals on the primary side of the coil (little wires).
The proper way to test a coil is on a diagnostic engine analyzer, but if you go to the library and find the manual for your car, you should find resistance specs for your coil so you can check its resistance with an Ohm meter.
I think you are starting to have a problem with the alternator (battery warning light). An alternator with excessive ripple voltage can cause the tack to jump around.
I had symptoms of weak spark in my '88 LXi Accord a few years ago. I also suspected the coil. A friend who’s a long time Honda mechanic said to first put a remanufactured distributor, which included the ignition module. Vavoom! She ran much stronger after that.
With the ignition off, set your electrical tester to Ohms. Between terminals A & D. It should be between 1.2 and 1.5 ohms. Between A and the secondary terminal it should be between 11,074 and 11,526 ohms. Between B and D it should be between 2,100 and 2,300.
If any of these measurements are out of spec, go ahead and change the coil. It might not necessarily be the main problem, but it’s good to eliminate it and they cost a whole lot less than a new distributor.