If your Toyota will not start when the air temperature or the engine is hot, there may be several problems with your vehicle. Worst of all is the scenario where you engine has overheated and is frozen due to the melding of metal parts from the intense heat and friction that occurs. Some problems can be easily fixed by you with a few simple tools, while some other problems may need the services of a professional mechanic.
Open the bonnet on your Toyota. Place your hand near the engine to feel how warm it is. If the engine is extremely hot, it may have recently overheated and shut off automatically. Allow for it to cool for 45 to 60 minutes to see if it is able to start up again. While the engine is cooling, check the reservoir for radiator coolant. If it is below the minimum line on the reservoir, use a funnel to add more 50/50 coolant or add distilled water.
Check the drivebelt's tension and deflection depth with a ruler if the car has been idling roughly or stalls out immediately after cranking. If the belt is less than 12 inches in distance between pulleys, check the deflection distance between the pulleys. The belt should have a deflection of about 1/4 inch. If the belt is more than 12 inches, the deflection should be between 1/4 and 1/2 inch. If the belt is too loose, it will deflect more. Tighten the adjuster pulley bolt with a socket wrench until the deflection reaches its proper height.
Use an OBD II scanner to check any vehicle codes that are showing up if the check engine light is on. A variety of sensors may need replacement or, if the sensors themselves are good, the electrical systems connecting the sensors to the engine control unit computer may be faulty. Specific sensors that may show up on the OBD II scan include O2, manifold absolute pressure sensor, knock sensor, coolant temperature sensor, air intake temperature sensor or the exhaust gas regulation sensor.
Replace the spark plugs if they have not been replaced within the past year. Remove the wires and caps to the old spark plugs. Use a spark plug puller and socket wrench to remove and install the new spark plugs.
Check the air filter on the Toyota, which may be dirty or clogged. If the air intake assembly is disconnected or jostled loose from the air filter box, the engine may not start when hot. Replace the air filter and inspect all of the air intake components to make sure they are properly connected.
Use an Internet search for Toyota recalls that may be related to stalling or not starting properly. Contract a mechanic to check other components of the car, including fuel injectors or coils. Also, the solenoid may also be too hot if the engine has been running hot during a summer day. This can be solved by installing a solenoid heat shield.