I have an older car, a '93 Geo Prizm, which I need to replace sometime
soon, but I'm still using till I'm better prepared for a new car
purchase.  In the meantime, I've been having various problems with it
over the past year or so.  One issue was the emergence of a growing
loudness in the engine.

Took the car to a new mechanic a few months back, and he found a loose
cable harness or something, which was rattling around.  He jury-rigged
something to keep the loose part in place, and that addressed the
noise problem somewhat.  

But then, yesterday, the battery dies.  Take the car to the same
mechanic, he puts in a new battery (tells me the old one was only
rated for four years, and I'd been using it for six).  Anyway --
getting to the point -- I could swear the car engine seems somewhat
quieter now that the battery is replaced.  

Is that just my imagination, or could a bad battery affect engine
performance, maybe cause timing or misfiring issues?  I don't know
that much about cars, but I would think that once the car is started,
it's running off the generator, not the battery, so a weak battery
should not cause problems.  But maybe there is something I don't know
here.  So please clue me in -- could a dying battery result in
decreased engine function/greater noise?

Thanks in advance for all replies!

Steve O.

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