Friends: Apparently in both vehicles the fault is the same, it is a failure in the idle control actuator. It is generally broken and when the vehicle is running, it opens to compensate for the deceleration, but it does not close again when the engine is left in idle, which causes the engine to be accelerated (and frequently tends to accelerate more and more).
The most appropriate would be trying to disconnect it after starting the engine to leave it fixed to those revolutions, as the engine should start with normal rpm and then accelerate due to the failure. The vehicle must be tested to verify if the revolutions of the same are normalized with the disconnected actuator.
All this is strictly as proof.
If so, you have to replace the idle control valve (IAC) to solve the problem.
If after that test the problem persists, the output voltage of the Lambda probe (oxygen sensor) that should be ranging between 0 and 900 MV must be measured. If the sensor readings will be fixed in a value means that the problem has another origin. If the oxygen sensor readings tend to 900 MV, the temperature sensor (CTS) of the refrigerant, the admission air temperature (IAT) and the air flow flow sensor (MAF or fluctioner) would have to verify.
If the oxygen sensor voltage from the moment of the start is fixed in approx 500 mv, then the sensor is defective and must be replaced.
It is important to know that the luminous witness "Check Engine" does not exclusively indicate an oxygen sensor failure (that has become a quasi-mit), but it is actually an indicator of failure in the engine control system, bone of all components of the electronic system, be it a sensor, an actuator or several of them. If the "check Engine" is turned on with the engine running, it means that some component of the engine control system is failing so the possibilities are very varied.
I hope my response will help you.
Greetings from Chile.
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