Why is my chevy venture high revs during idle after temperature starts to rise

try injector cleaner or newer fuel cleaners, try octane booster, sounds like a fuel delivery symptom but the temperature factor is a worry. I would guess injectors.

This is normal. The ECM monitors engine temperature and increases idle when it sees the engine is cold. The ECM sets the idle back to normal when engine temperature rises.

Your toyota technician should know what a "cold starting solenoid" is. It is the little thing that works your throttle until the motor warms up and something else takes over. I'd suggest going to another technician.

vacuum lines has leaks. also, have your MAF sensor cleaned.

If the vehicle is an manual gearbox, hold the clutch in until the engine has taken properly. If it is a manual rather start i neutral with the park brake on than in Park. Once the engine has started, let it idle for a minute or so before driving off slowly. Until the temperature gauge has at least reached the 1/4 mark, try keep engine revs below about 2500. All the while keep an eye on the temperature gauge, if it rises very sharply and the fan does not come on, there is a possibility that the radiator is frozen and the engine will boil and burst a hose. If the temperature does rise suddenly, stop and carefully feel if the radiator is still cold. If it is, shut off the engine and wait till the radiator has thawed. This will take a while but can be hastened by starting the engine for a few minutes to warm the engine compartment to help thaw the radiator. When water is circulating freely, you should see a sudden drop in temperature. Do not rev the engine too much, the incoming water will be ice cold and could crack something. This is not something that occurs often, especially if you try park the car where air cannot readily blow through the radiator overnight.

http://autorepair.about.com/cs/generalinfo/l/bl703.htm

Chevy made some weak intake gaskets on 3.1 and 3.4. My guess is that the intake gasket is weak and/or leaking and it is letting pressure out somewhere. At idle maybe the system pressure is to little to push hot coolant into the heater core.

distributor is advanced

the idle air contoller,or thecoolant temperature sensor,which when cold sends info to the ecu to idle fast

If you are still using the carb engine check the idle up, there is the carb's version of a fast idle control. Some carbs would have a lever that pushes the throttle a little higher during start up. There is a screw there that you can adjust.

If it is an EFI engine, if you are experiencing very cold temperature, your car maybe compensating.