Originally Posted By: yeehaw1960
I'm thinking that, since the engine ran smoothly at higher RPMs, the 5 1/2 year old battery may have contributed to the weak ignition coil not firing at low RPMs. Thoughts? I could be, and often am, wrong.
Nope. Your car's electrical system, once started (engine running), it's supported by your alternator and not your battery.
In other words: your battery is primarily responsible for starting the engine.
so long as your alternator functions properly and able to charge your battery (>12.6V DC, mostly over 13VDC under most conditions), your electrical system is considered healthy.
Weak coil has nothing to do with that. look elsewhere.
Q.