Bad battery and engine noise

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Steven O. - 23 Feb 2006 04:48 GMT

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.

"Spying On The College Of Your Choice" -- How to pick the college that is the Best Match for a high school student's needs.
www.SpyingOnTheCollegeOfYourChoice.com

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Don Bruder - 23 Feb 2006 06:20 GMT

<snip.>

> Is that just my imagination, or could a bad battery affect engine
> performance, maybe cause timing or misfiring issues? I don't know
[quoted text clipped - 3 lines]
> here. So please clue me in -- could a dying battery result in
> decreased engine function/greater noise?

Damn skippy it could.

If the alternator is trying to pump up a battery that doesn't want to
take a charge, and the battery is low to begin with, that can easily
mess with the strength of the fire at the plugs. If it's FI, the bum
voltage may have an impact on fuel pressure to the injectors, possibly
cause a "sluggishness" in them injecting or how "cleanly" they
open/close for the injection. Might also impact sensor readings from
items expecting "at 12 volts of input, this condition makes me put out
X.y volts to the computer", causing a mis-read of thae actual situation,
and making the computer bollix the mix to be rich or lean, or perhaps
jiggle the timing in an effort to compensate for the (seemingly) wrong
running conditions the sensors are reporting, with resulting impact on
how it runs, and probably other things besides. Those are just the most
obvious scenarios I can come up with. I imagine others will be able to
add to the list of ways things might go weird if a battery is on the way
to dying completely on you.

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Kevin - 22 Apr 2006 03:11 GMT

Basically... NO..... a bad battery will not cause an engine to run bad.
Well, let me specify that a battery that is good enough to crank the engine
will be good enough to not cause any performance problems other than a
slightly increased load on the engine, to try and recharge the weak battery.
All the systems will operate on less voltage than it takes to crank the
engine. Now, if the alternator is bad and the battery is bad then you might
run into a situation where the electrical components are affected by low
voltage to the point of causing engine performance problems. At that point
if you turn off the engine the battery will not have enough voltage to crank
the engine. The injectors need at least about 10 volts to work the ignition
coil needs about 9 volts minimum but the computer system can run on as
little as 5-7 volts. So let me clarify. Once the battery gets to a point
where it will not even crank the engine, then it cold cause poor engine
performance, but not until it reaches that point.

Kevin

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Kevin Mouton
Automotive Technology Instructor
"If women don't find you handsome, they should at least find you handy"
Red Green

> 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
[quoted text clipped - 27 lines]
> "Spying On The College Of Your Choice" -- How to pick the college that is the Best Match for a high school student's needs.
> www.SpyingOnTheCollegeOfYourChoice.com

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