Jul 11, 1998
RAY: You're driving home from work one late afternoon, one of those middle-of-winter types where it seems to get dark shortly after noontime. You've got a long commute, maybe an hour or so, and you notice that as you're driving along the engine is missing...
TOM: You mean somebody's taken it?
RAY: Not quite, I guess misfiring is the proper terminology. Anyway, it's just running poorly -- no power up hills, coughing and sputtering. When you're on level ground, it seems to run so-so, but up hills, urpp,rupprupp, rupp, urpp is what you get. Oddly, it doesn't seem to have the power that you recall it had that same morning on the way to work. You think you might need a tune-up, but aren't quite sure. Then, as total darkness approaches, you turn on your headlights -- and notice in the process that the engine misfiring gets decidedly worse. Question: What kind of car is this? Only kidding. Real Question: Part A: Are you going to make it home? Part II: In all likelihood, what is wrong with this car, and how are you going to fix it?
RAY: The answer to Part A is, unfortunately, probably not. The reason being that at some point along your journey, your charging system has stopped working, causing you to run solely off the battery.
As the battery weakens, there is less and less juice available to fire the spark plugs, creating a weak spark and causing the engine to run poorly.
This is also why the situation worsened with the headlights on, when the available electricity was divided further between the engine and the car's running systems.