Rough Idle Because of Alternator?

[Anonymous]

Hi Guys, havent posted in a while but right now im having trouble getting my stang to idle smooth, been trying for a while now right now its idleing at 700ish and itll pop and shake not to bad but enough to notice readily. also ive noticed that if i have my dash lights on itl will dim a little when it does this, when i give it gas it runs great no prob what so ever its just at idle in gear and out, in gear it is worse but the idle is a bout 600.

its stock 80 motor with a msd ignition,

 

[rbohm]

8) it's very possible that you have a bad alternator. take it to your local auto parts store and have them check the charging system.

 

[CobraSix]

I think you may have something wrong with your tuning that is making the alternator not get enough power from the engine and thus giving the impression it is not going well.

But...always start with the easy stuff first, it could very well be the alternator, so go to an local auto store and check it out.

Slade

 

[Anlushac11]

I think you may have something wrong with your tuning that is making the alternator not get enough power from the engine and thus giving the impression it is not going well.

Slade

Err?

I could be wrong..god knows its happened once before in my life

All the engine does is provide the mechanical motion to turn the alternator using the belt while there is a electrical charge going through the fields. If the alternator is bad and not charging or is hooked up wrong, then the electrical and ignition system will draw from the battery. As the battery gets weaker it can cause the engine to start running rough as there is not enough juice to charge the coil.

 

[CobraSix]

After I posted that I went on my morning run and thought about it and it didn't make sense to me either. Must have been the morning haze.

But, I would think the Alternator warning light would light up if there was a problem with it. I've usually found those lights on any car the only warning light that works consistantly.

My gut instinct still tells me the rough idle is a tuning issue and not a charging issue. But then there is the light diming portion of it, which makes me think the alternator has a problem. I don't necessarily think to two are related though.

Slade

 

[Anonymous]

hmmm, ive seen the alt light blink on a off again every so often it dont happen much. but every once in a while itll blink on then off fast. its been this way for a while now, it wont charge my battery with the lights fan and wipers on.

 

[CobraSix]

That is either an alternator or Voltage Regulator problem. To avoid replacing both before figuring it out, take it to an autostore that has the free electrical system test and see if your alternator is bad. Or, you can take the alternator off, go to the store, have them bench test it. If it is all set, get a new voltage regulator, if it is bad...you know what to get.

I just don't think the two issues are related. Even my MSD Digital 6+, Pertronix, and flamethrower coil can operate correctly down to 7-9 volts. At that point, you wouldn't be able to start your car...so I don't think the two problems are connected.

Slade

 

[rbohm]

8) we found many times with the race car, even with a unilite ignition which is like the msd in that it can run on 7-9 volts, that if the battery was not fully charged, we had a miss when making a run. even the high dollar ignition systems dont like low voltage. while they run, they dont do so efficiently. my guess is a bad diode or two in the alt preventing it making full rated current, and that is what is causing the problem, but like mark i have been wrong before.

 

[Anonymous]

check for bad/worn wires. I had a bolt fall off the back of the alternator...while the wire was on, it wasnt making constant contact....thus I didnt have a full battery.