May seem like an odd question, I have been having a problem with misfire, the truck runs horrible with no power. I had a friend come over to see if he could figure it out, being that my battery dies if i leave it hooked up (have yet to find the cause of that problem) i hooked up the cables and we took off. At the end of the street my friend noticed that the volts were really low, at that point the truck was running fine, i pulled over popped the hood and noticed i forgot the charge lead for the alternator. We got that hooked back up and took off and it was running horrible. So we tried unhooking the alternator again, fired it up and ran perfectly fine. I swapped the alt with a known good one, same thing, i loomed up the plug wires and pulled them out of the way (they were touching the alt before) same thing. It only runs good with the alt charge lead unhooked. Has anyone heard of this? Any possibilities?

 

You may have a near dead battery and when you hook up the alternator it puts a load on the engine. You would believe the load this puts on an engine. An alternator is not suppose to charge a battery only maintains the charge. You need to charge the battery with a battery charger and check the voltage at the battery with it running.
You can smoke an alternator if you try to charge a dead battery with it.

EDIT:
What wire are you hooking and unhooking?

 

sometimes when you drain a battery low, it wont charge back fully to 12-13. running, it should run 14-15. across the terminals.

Also check the belt, see if thats loose, or worn.

Take the distributor cap off and see if theres any build up under it. plug wires need to be snug when on, not loose. Fill the plug boots up with dialectic grease.

also, check and see if you have a bad ground. take the negative wire off, and hook the light tester on that wire terminal, and a part of the body.

 

I am unhooking the charge lead off the alternator from the (+) side of the batt, and for reference it's a 3G. Plug wires are new, cap and rotor are new, belt is also new, no slipping. Might be low voltage, but i have had it run down lower before and it never caused this. I'll try a different battery tomorrow, and I'm also going to add a few more grounds. It's only under load with the charge lead of the alt hooked up which makes me think the operation of the alternator is causing a misfire.

 

any more ideas?

 

Did you ever find out what was the issue with the Changing and Misfire I'm having to same issue. Thanks

 

The thread is well over 15 years old. And the OP hasn't posted in almost 14. You're not likely to get an answer. Start your own thread, list Year, Model, and drivetrain and ask your question, it will probably work better.