I have a 1991 4runner 3.0 auto 4X4. When the outdoor temp is below 50-55F (above freeziing) my 4 runner does no warm up enough to go into overdrive. I have a new OEM thermostat and radiator cap. Also new solenoids, filter and fluid in the trans due to one of them not working. The coolant is new and a 50/50 mix. This thing runs just fine when it is warm outside. I can leave it running in the morning to warm up for 30 minutes and that makes no difference. I drive mostly highway. I did notice that if I drive around the city it will shift just fine due to stop and go traffic. If it does warm up enough on the highway to shift into overdrive it will come out of overdrive as soon as the thermostat cycles. The heater works just fine as well. The only thing that leaks is the steering box.and the sunroof.

There are no engine codes, smells or noise's. It will literally drive flawlessly when it is warm outside. There is no body modifications to the frront end to change airflow through the radiator. I have even tried covering up half of the radiator to try to get the engine temp up. Granted that the stock temp gauge is not accurate, it does not move past 1/3. Under warmer temperature conditions it moves up to the left edge of the thermometer icon in the center of the gauge.

I have all of the FSM's and have performed most of the troubleshooting in there with no help.

Thank you for your time.

 

Your dash gauge and ECU use the different sensors, on the 3vze these are located next to each other. You can start with cleaning the sensor and its housing and ensuring they have a good ground connection.

 

I bought the sensor but cant get to it. Is there an easier way other then pulling the upper plenum off? I have fairly large hands that do not quite fit behind there....lol