What are the symptons of a duraspark II ignition module going bad?

I know of the ones such as no start, or dropping dead. But I have this slight misfire at idle that comes and goes typically its only when in gear and most of the time its with the engine at full operating temperature.

Today though from a red light after I stopped off at advance for UV dye, I drove for about 3/4 of a mile and was stopped at a redlight, when the light turned green I stepped down on the throttle harder than usual and the engine started missing like I was running out of fuel but quickly straightened up smoothed out and accelerated fine. I tried to duplicate this problem and I could not.

The only things that I can think that could cause this that I have not replaced would be the ignition module, the dist. and the plugs. I replaced the cap and rotor earlier this year, the spark plug wires were replaced back in 2006. The dist. and the ignition module are both factory orignal pieces from 1978 and have never been replaced. The spark plugs I assume were replaced at one time but I never replaced them.

So I dont know if the misfire at idle that comes and goes when in gear is just the engine since its pushing 200,000 miles, or if its ignition related that is starting to go out. I know if I idle the engine up it does not do that miss its only when I am idling around 600 RPM which is still too high for this engine as the idle speed is supposed to be 550 rpm with the AC off and 625 rpm with the AC on.

So I am asking what symptons of a intermentant malfunction on a Duraspark II module? The car hasnt dropped dead on me and refuse to start, the dropping dead was before I got the final kinks worked out of some misadjustments in the carb that would cause a stall if the engine was cold.

 

Remember, the duraspark module runs ALL the sparkplugs. When it throws a fit, the engine has a serious problem, and that's why it usually dies. Your slight miss-fire definitely could be worn plugs. I would change them.

 

Your issues sound like a fuel delivery issue and not related to the ignition. They most certainly do not point to the ignition module.

To answer your question directly, the most common symptom of a failing module is for the engine to cut off completely. Once the engine cools off briefly, it can start again. There is hardly ever anything in between.