Engine stutters when headlights come on

[Yaddle]

I've got a strange problem. My 87 4Runner's 22RE stutters nearly every time I turn the headlights on. For just a second it seems to miss a spark or two. It's a brief but pretty severe drop off, enough to see the RPMs drop by a couple of hundred on the tach. I just sort of shrugged it off until it nearly killed it entering the interstate a few days ago.

The battery is only a week old, and it did this with the old one, so I can eliminate that. I've also already replaced the wire that runs from the positive battery terminal to the fuse box with a piece of 8 gauge battery cable.

Has anyone experienced this? Any of you T4R gurus have a clue what could cause this?

 

[Iroke17]

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[fourwd1]

... I've also already replaced the wire that runs from the positive battery terminal to the fuse box with a piece of 8 gauge battery cable.

Check the rest of the pos and neg (ground) wiring to be sure the connections are clean and tight.
Alt to battery +, battery - to body, body to engine block, body to frame.
The next thing to consider is the alt itself, are there any other signs that could point to a problem with it?

 

[echo4tango]

it could be a weak/bad alternator?