[BrandX]

What would cause this?

My car wont idle on its own when the alternator belt is hooked up? Check it out, It idles fine and you dont have to touch the gas with no belt. You hook the alt up and all the sudden it starts loading up and i have to keep cleaning it out. Sounds crazy huh? I dont get it either. 2 different alternators and the same results. I am gonna try to get some big stereo cable and run it all the way to the battery tomorrow. For now it has 12 guage wire running from the alt to the ford solenoid on the firewall. I wouldnt think this would be any different, considering that it is hooked up on the same side as the main battery cable.


Any other ideas?

[hal101]

i think the alternator is puting a load on the motor slowing it down as it charges the battery

[ponjohn]

What ignition?
Internal or externallly regulated?

If external could very well be a bad regulator generating electrical noise screwing with the ignition.

If you're handy with a voltmeter, connect alt and measure voltage at back of alt then on ford solenoid. Should be minimal difference if at any. This will give you a good understanding if the wire is faulty or undersized.

[Geronimo]

Brandx,
I think there are two possibilities? 1 your voltage regulator is stuck in full field mode causing extreme mechanical resistance and high voltage. 2 Your ignition coil is hooked up in reverse polarity or coil/ module is breaking down and misfiring when system voltage increases more than battery voltage.
Your battery is fully charged around 12.65 volts, a correct working charging system should produce a minimum of 13.2 volts to a maximum of 15.5 volts at 2000 rpm. Most hang around 14 volts. Check your voltage at the battery or at the a/c generator while the engine is running aroung 2000 rpm. If it is over 15 volts I would suspect the voltage regulator. If the voltage is within specs, You must have an ingnition component breaking down at anything higher than battery voltage. It happens more than people realize.
Geronimo

[BrandX]

it is internal regulated. I will do some volt meter testing today and post my results.

[screamingchief]

Have heard of more than a few guys getting serious interference in their bugzapper boxes via the alternator,in most cases a proper noise filter on the box power supply lead cured the deal.

[goatracer]

Well guys... add me to the list also. Just put one of those Powermaster 100+ amp'rs on my new motor and now I have the same issue! Maybe I'll try one of those filters like SC mentioned.
Bryan

[ponjohn]

I would also try with a good heavy cable, grounding the alternator to different parts of the engine compartment. If available try a second battery powering the ignition by itself. It might be necessary to ground the negative side to the car. See if problem persists.

Those alternators are obvioulsy very noisey. You can also buy filter capacitors at radio shack. try .1 or.01 uf (microfarad) and a .001 uf. Install them at the output to ground and/ or on the supply to the ignition box.

Install them with the leads twisted together side by side (paralell) not inline (series).

You might also need a choke (coil) to supress the noise. The capacitors are a cheap try.

The BEST method is to (if available) put an oscilloscope on the output of the alternator and see exactly what the alternator is producing.

[Geronimo]

I always assume people have adequate grounds and or shielding. If you have some aftermarket ingnition controller, it could be the victim of electromagnetic interference or poor grounding. Batter negative to the engine block and core support, cylinder head to firewall, and engine block to frame shold provide adequate ground. Any input wires to the ignition box can be protected from EMI by placing grounded wire(s) along the input wire(s) taped or ziped every few inches and hidden in loom. Only one end of the shielding (drain wires) needs to be grounded. If your ignition box is still acting screwy, you may want to put a capacitor in parallel with its power wire. These are sold as a noise suppressor or RFI capacitors at radio shack and such. Normally your battery serves as the best capacitor smoothing out the ripple current from your a/c generator.

Hope this helps,
Geronimo

[wrench]

I am sure you checked this, but what about the extra voltage to your fuel pump causing too high fuel pressure? I guess there would have to be something wrong with your regulator, but worth a check.

[OINK 1]

HEY !!! TURN UP THE IDLE !!

[TheMonkey]

in a traditional, non-ECU car, i don't suspect noise is your problem. as suggested, check out grounds.

i have an ECU on mine, and some sensors are very particular to noise issues. FWIW... here is what some capacitors did to my power bus. cut some info from an old post:

see frequency with each spark event:
-the ignition system includes an MSD 6AL box. here's a before pic of power without alt belt connected, and no o2 sensor: i installed MSD capacitor 8830 and swapped coil from Blaster HVC-2 to Blaster3, and the power cleaned up like this.

see very high frequency from the alternator brushes:
-the alternator is new and had very mild spikes in this before pic. i had an old HEI distributer, and swiped the .25mf capacitor from it, put it on the alt, and it cleaned up nicely like this.

these type of noise problems will be magnified with poor grounds. capacitors might fix your problem, but i would start checking all grounds.

[sleepy]

Turn up the idle another 50-100 the alternator will put a lot more drag on the motor than you think. especially if it's charging at a high rate.

[tiacguy]

Check the diodes in the alternator. A bad one will cause AC to bleed into the DC current system and cause problems with the ignition system.

[BrandX]

I turned the idle screw 4 turns and still wont idle right.....It aint that....It has to be one of my grounds. Last time it was running it was perfect...It just started this since i put new head gaskets on it. (had the motor out) .....

[sleepy]

do you have a volt or amp gauge in the car? If you do what does the gauge read with the belt on. is it possible you have the alternator wired backwards? or the power wire grounding out?

[goatracer]

Just found broken #1 plug. I was trying to turn up the idle as well and found the plug arc'in against the head. Probably broke it when I installed the engine I would guess. I'll see if that fixes things.
Bryan

[goatracer]

Well replaced the plug and adjusted the idle. Seems to be all set now.