Ok, my 350 TPI IROC has been idling rough for some time and suffers a power loss and general crappy driveability up to about 2800RPM. I have been through the whole ignition system and replaced everything from the coil to the plugs and it didn't help. The fuel system is fine and I have checked most of the control system as well. What makes me think it may be the alternator is that when I put an accessory load on it, like rolling down both windows at the same time, the voltage gauge dips and the lights dim and the car shudders and almost dies. Even my turn signal makes the voltage gauge tick up and down a few volts. When one of the cooling fans comes on it sufffers a sharp dip as well. Can my alternator cause these symptoms, along with driveability problems? Thanks guys, sorry it's so long.

Yes it can. If you are suffering from undervoltage, so is your fuel pump....It could also be your battery is on it's way out, but it does sound like a bad voltage regulator and/or alternator(might just need brushes). I would have the alternator and battery tested, if you can't do it yourself.

I had the same problem when my alternator was going bad. Even to the point where it was hard to start the car. You can use a voltmeter to test your alternator. With the car off, you should read around 12 volts at the battery terminals. Then, start the car. Again measure the voltage at the battery. Your voltage should be around 2 to 3 volts higher than your original reading. Then you can turn lights on, wipers on, radio on, hazards on, heat or a/c on... now measure the voltage. If its battery voltage or less, then you know your alternator isn't charging your battery. This is about all I think you can do without taking it to a repair shop to have it load-tested.

Oh, one more thing... make sure the alternator belt is REAL tight. Did you use a crow-bar to tighten it? Just pulling the alternator with your hands to tighten the belt is never tight enough!

Joe


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86 IROC TPI
700-R4
K&N Air filters

Thanks guys. I didn't know an alternator could make one run like a@# but it makes sense that it would. I'll check the battery out too while I'm at it. Just put a new belt on and it's a serpentine system, so I don't know if that's the problem or not.

Well Jethro, you know what I think already.

back when I ran TPI (computers..eek) and put on a real underdrive pulley (moroso 3") I had problems sitting at stoplights when in gear. The voltage drop was too much.
Then whenever I was racing and using an alternator-kill switch the engine would sometimes stumble and flash the SES (check engine) light at me. My solution at the time was to run a Jacobs Accuvolt to supply voltage to the ECM, ignition, and fuel pump when I was racing or holding the brakes. This worked out great which tells me that ECM's, ignitions, and fuel pumps like a steady voltage supply.

With your alternator, maybe the internal regulator (I always run external) is getting flakey from the heat. I would also expect a failed or failing diode inside.

Oh and when you go to tighten the belt, definately use the leg off a swingset to pry with until you hear the rear-mains cracking. This takes a lot of slop out of your crankshaft which should also raise your oil pressure. If you're lucky the crank will bend some in the middle giving you more stroke on the middle cylinders.
(just kidding for those that don't know)

ODB

Thanks for all the help, man. Looks like I'll be shelling out $100 for a new alternator soon. Come to think of it, the little indicator on the battery shows black a good bit of the time, so that may be part of the problem too. Funny thing is that it's never left me stranded before.

did you try a different battery yet?

defective batteries can damage electronics in the alternator like the diodes.

I know,
this further complicates things.

Yeah, guess I'd better pull the new one out of my truck and see what it does in the IROC. But if the alternator is already on its way out it might not make a difference. Time to get out the checkbook and head over to Sears. They can test the battery for me so at least I can see if that's the problem. Thanks for the help, ODB.