As best I understand it, the computer compensates for things that
can effect, for instance, mixture.

When I had front end work done on my Blazer, the battery was disconnected
for a couple of days. The computer lost all the settings it had been using
to control mixture. The throttle had "stuck" a couple of times; didn't back off
when I took my foot off of the gas.

No codes thrown - just normal accumulation due to age and mileage (he said).

When hooked back up, the car would not keep running at idle.
It died in seconds.

The mechanic working on it said that told him exactly what the "stuck throttle"
problem was - some kind of accumulation in the throttle body. He opened it up
and cleaned it out and it ran fine.

After a month, it started doing it again, so I added a bottle of Gumout Fuel
system cleaner to the gas at oil change time - and it hasn't happened since.

All this because the stepper motors that control mixture and throttle were
getting gummed up and not positioning correctly and the computer was
compensating to try to keep the engine running. When it lost settings, it
just couldn't run at all.



That's as best I understand what he told me anyway...

Richard

spaco wrote:
Do you mean that if you were to replace the battery in your car, it
wouldn't run? Or do you mean you'd loose error codes?

If I take my car in for service and they do certain kinds of work, it
comes back with the radio stations lost, but the engine runs fine. Do
they put the engine settings back?

If the alternative was a dead battery, then what's the difference?


Another point about what causes batteries to discharge when not in use:
I have heard that some cars have "cathodic protection systems" to, I
guess, minimize rusting. That must take a fair amount of current, too.

Pete Stanaitis
-------------------

cavelamb wrote:
Pete,

Reconsider the battery shut-off switch on any vehicle that has a computer
to run the engine.

Disconnecting the battery will cause the computer to lose engine
settings.

And THAT can cause all kinds of wild problems when you hook it back up.