I have a 1997 4runner, Manual transmission, 4WD, V6.
Within the last 6 months or so, I have experienced three instances where it started up, but I noticed when I started driving, even though the RMP's and engine seemed like they would behave like normal, it didn't seem to be affecting the actual acceleration.
Basically, I could floor it in any gear, and it would continue to accelerate at the same rate through every gear and RPM it seems. I would estimate it would take me a good 15+ seconds to accelerate to 40 MPH. The sound of the engine also was definitely sounding different, pretty much a higher pitch, and just "off" from the normal healthy engine sound.
I was not overly concerned at first because this issue was so rare, and I found that it was easily fixed by turning off the 4runner, and then turning it back on.
However today, this issue I believe has become a problem. Today, I had the same exact symptoms as the other time, however this time when I tried to restart the 4runner, it tried to start itself.
Basically, I turned off the engine, took my key out, and it just sat there sounding like it was trying to turn over, as if I was turning it over with a low battery or something. It was doing this for several seconds before I turned the car back on, afraid it would cause some kind of damage if I left it like that. The sluggish issue described above continued as I limped a few miles home, and twice more I tried to turn it off and take the key out, with the same result. I then decided to leave the car running while I consulted my friend about this situation, and was about to yank off the battery cables when the engine went back to its normal sound, and then I was able to turn it off normally.
I opened the hood, and was checking for any issues, of which I saw none. I know a little bit, but I don't know what to look for beyond something fairly obvious. The only thing I noticed was a little bit of smoke (barely noticeable) coming from, I think, below my power steering fluid area. Also it did smell kind of like electrical burning.
I haven't tried to turn my car back on yet for fear of causing further damage.
Also, a possible related issue, within the last couple of months I have had an increasingly hard time starting my 4runner. Starting at maybe one out of 10 starts I had trouble, to now I probably have an issue 60% of the time. This isn't a huge deal, as I usually only have to turn it over twice and it will fire right up. I was planning to have this checked out before too long anyways.
So I don't know if anyone here has any answers, but I would love some insight into what I'm dealing with.
I was at a mechanic maybe three weeks ago and I had them look at the starting issue, and they couldn't reproduce it so they weren't sure.
Any info would be incredibly helpful! Thank you.

 

Do you have a CEL on? I would think whatever is causing your low power should trip a CEL. Your engine continuing to run sounds like it's "dieseling". Are you familiar with that? The engine keeps burning left over fuel and carbon in the cylinder and deisels (fires without a spark). As far as it not starting, you mean you turn the key and nothing happens or maybe just a click, and that's it? If so it's probably your starter contacts need replacing.

 

I've seen alternators short out before and they do something like this basically the alt. becomes a motor and continues to keep turning the engine over after its off and while the engines running the alternator resists being turned by the engine it usually looks pretty obvious if you look right at the pulley but our alternators are pretty buried in there and with a serpentine belt it makes it a little harder to see good luck buddy hope this helps you

 

Could be a loose wire that when its hot makes contact completing your ignition circuit. May be a short due to corrosion.