Why does the engine speed remain high during cold starts in summer?
2 Answers
There are mainly the following reasons for high engine speed during cold starts in summer: 1. Generally, the idle speed during cold starts tends to be higher because it varies with ambient temperature. It's normal for cold start speed to remain within 2000 RPM. 2. During cold starts, the engine speed is automatically adjusted by the ECU based on signals received from the coolant temperature sensor and oxygen sensor. When the vehicle's computer detects changes in coolant temperature or variations in the oxygen sensor's feedback voltage, it continuously corrects the fuel injector's fuel delivery quantity. Therefore, before the engine reaches optimal operating temperature, the ECU's continuous fuel adjustment causes corresponding fluctuations in engine speed.
High RPM during cold starts in summer is something I've encountered many times over my 20 years of driving. Mainly because summer heat makes the air thinner, and the engine's computer automatically injects more fuel to maintain the air-fuel mixture ratio, which raises the RPM. Excessive carbon buildup in the throttle body can also restrict airflow, leading to high RPM. I regularly clean the throttle body to prevent this issue. Additionally, faulty sensors like the intake temperature or oxygen sensors might mislead the computer, so they should be checked. High RPM not only increases noise but also fuel consumption. I recommend parking in the shade during hot weather and waiting for about a minute after starting until the RPM drops before driving to ensure safety. Don't underestimate it—it can damage the engine.
