Alternator issue . . .

97 Tacoma 3.4l, 250k miles

A couple weeks ago an old issue with my truck popped up again. While driving and on the accelerator, the engine will for a split second lose power and then jolt back. Back in April I was having this problem and it turned out to be a bad alternator. I bought a replacement from NAPA and haven't had issues until now. Brought the new alternator back to the store, they tested it and it failed. Got a new one on warranty, put it in, and everything ran great for a day (maybe 30 miles of driving total). Very next day the issue is back, especially after a cold start, and my idle's running high at about 1000 rpm. It's a little bit better when the engine's warm but still present. I disconnected the battery, waited twenty minutes, and reconnected. The idle was now low, about 600 rpm, but after tapping the gas it settled right at 750. But the quick jolting from the engine kept up and the high idle came back after another cold start (tried disconnecting and reconnecting battery a couple more times with same result). Took this alternator to NAPA. They said it wouldn't even do the load test so something is definitely up with it. Unless the replacement alternator I received was bad from the start, I'm worried the truck could have an electrical issue that's killing alternators. Battery tested fine. Where should I start looking for an answer?

 

I suspect bad parts, this is plaguing the industry.

The shutting off driving, a bad alternator shouldnt do that unless you were driving off the power stored in the battery because the alterntor isnt charging. The first thing I would check is the ALT fuse in the engine compartment fuse block. This fuse bolts in and you have to seperate the top and bottom of the fuse block to access it. I have seen the filaments broken, by passed and just plain 'ol rigged. I keep an extra fuse in the glovebox just in case.

The idle "thing" is normal. When you disconnect the battery for a period of time the PCM resets back to factory settings and has to relearn from inputs as you drive.