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Discussion Starter · #1 ·
hey, what's up?

I have a 1991 LX (automatic) and I was wondering why my battery voltage meter and my RPM tend to go up and down while I am stopped at a red light. When I come to a red light, my battery voltage goes down a litte bit and then goes up to normal and repeats this until I start accelerating. My RPM goes down along with my battery voltage. My car stays on but my engine does not sit at a normal idle.


Any ideas as to what it could be or what I should check?
 

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josegome said:
Any ideas as to what it could be or what I should check?
You've gotta learn how to demand nothing from your alternator.
You pull up to the light, your RPMs go down, your alternator spins slower, you have less voltage and you're discharging your battery. The automatic holding your revs down even further, makes it worse.
You could buy an underdrive pulley kit, and install only the alternator pulley, or you could go with a bigger alternator(130amp or more).
Of course, you might see an improvement by simply replacing your battery cables, if they're old and grungy.
 

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You could also have a problem with the idle air bypass and/or the throttle position sensor. If the RPM will settle down, so will the battery charge voltage. Clean the idle air bypass and see the post above on how to set the TPS sensor voltage.
 

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probably your alt.
my 88 was doing the same thing, and i replaced the alternator it its all gone. it does it every once in a while, but i have a bad tps as well. so i think thats it.

also, you may want to do the ground strap upgrade stickied in the tech forum.
 

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maybe maf,or tps,vacum leak.good luck
 
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