Extreme Mechanic Solutions

Toyota Voxy

Problem very high idling rpm 1500rpm + and stalling sometimes

Checked PCV valve , damaged intake line, malfunctioning EGRV, damaged brake assist(vacuum) all was good.

Here is how your car works, besides your input through the accelerator your car depends on sensors to determine the amount of fuel to deliver to the injector,these are MAP, MAF, IAT , coolant temperature sensors, etc.

The engine works best when it acquires the normal working temperature, this temperature is detected through the coolant temperature sensor. So to achieve that temperature quickly the ECM is programmed to accelerate the engine to a predetermined rpm mostly 1500rpm so that it quickly attains the working temperature after which the engine rpm automatically declines to between 500 and 1000 rpm in idling.

Therefore if the temperature sensor is not working properly there is no way for the ECM to know the temperature of the coolant hence it will keep the engine continuously running at 1500rpm.

The best way to solve this issue is with a diagnostic
machine as it will take you to the exact problem without wasting more time. From the diagnostic I searched for fault codes and found two codes,one for the IAT and the other for the coolant sensors . Sensors exhibit different times of problems so to verify I had to open the data stream for the engine ECM. I selected IAT and coolant sensors and both sensors returned -40° F , which is a default temperature when there is total signal failure from the two temperature sensors.

To confirm that the vehicle was getting stuck in the warming up phase at 1500 rpm , I had to do another check, on data stream I checked for idle signal(IDL SIG). After running the engine for a long time it remained on OFF,meaning the ECM wasn't commanding the system to go to idle.

So now the information was clear, the car was getting stuck in the warm up phase at higher rpm because the ECM wasn't getting the required signal from the temperature sensor so process as idle on(IDL ON) signal which will return the engine to low idle rpm.

After thorough checking, found the problem to have been an open circuit on bought sensors, fixed the wiring and the idling is now at 500-700rpm