86 22re 4runner automatic

Hey so I've been trying to chase down an issue, the car runs underpowered when at temperature. When I first start it, it runs fine but idles a bit rough. Then when it's at temperature (or after driving around a while) it starts to have weak power. Like it'll have a hard time getting up to speed from a stop, and then once at highway speeds it often feels like from 1/4 to 3/4 throttle makes no difference. Also the automatic transmission struggles to shift sometimes with this lack of power.

So one thing I noticed is that my temperature gauge seems a bit low. I remember it used to go up past 1/2, then the thermo would kick in and would go down to about 2/5 and stay there for the rest of the ride. Now it slowly crawls up to 2/5, never really passes that. Sometimes it takes really long to get there.

So I'm thinking maybe my thermo is stuck open. I'll change it when I get a chance.. but the question is.. could this cause running issues? I know the ECU takes signals from a few sensors to determine the mixture. I've tested most sensors and they seem to test fine. Could a cold engine temp cause a bad mixture?

 

Bump.

No knowledge on running temperatures on fuel/air mixture?

 

Your MPG would suffer slightly if engine never reaches operating temp, but I would say you have another issue going on.

 

It will affect how it runs. It happened to me. I usually get around 17 or 18 MPG but on one tank I got around 12 or 13 MPG. This was strange so I started investigating. I checked the codes, there was a code for the engine coolant temperature sensor, so I replaced it. The light never did light up while driving, so I had no idea until I checked. If the computer thinks the engine is cold it will stay in open loop and keep things rich. I didn't notice any loss in performance though, so there's that.