Today, the weather cooled off a bit. I think it was in the 70's for most of the morning. In not sure if it's related, but my '91 4Runner seemed to run a lot smoother and felt peppier than normal. Also, it idled at about 750-800 RPMs where normally it runs around 1000. I also noticed that my subwoofer had quite a bit of extra thump to it.

It just felt, drove, and sounded better. Do you think it could have an electrical problem that's affected by the temperature? Maybe a weak alternator or voltage regulator? I'm just thinking that the heat might affect voltage output and cause it to run rough.

 

Cooler air + more efficient engine.

 

That makes sense. I guess that's the whole idea of a cold air intake, huh? It just seems like it's ran the same for several months, and then today it was better. I don't remember it being any better before summer started either.

I also forgot that I swapped out my dino oil with Mobil 1 synthetic last week. I wonder if that has anything to do with it.