What is the reason for the idle speed not dropping below 1000 RPM after warming up the engine?
3 Answers
The reasons for the idle speed not dropping below 1000 RPM after warming up the engine are: excessive fuel injection, excessive air intake during idle, and incorrect engine control signals. The method for warming up the engine is: after starting the vehicle, let it run at idle for 1 to 2 minutes until the engine coolant reaches normal temperature, then you can drive. Solutions for excessively high idle speed: 1. Adjust or replace the throttle position sensor; 2. Clean or replace the idle speed control valve, and use a decoder to perform a basic idle speed setting; 3. Locate the leak, reseal or replace the relevant components; 4. Check the timing marks and readjust the valve timing according to standards; 5. Clean and inspect the fuel injection quantity of each injector to ensure there is no blockage or leakage; 6. Replace the three-way catalytic converter; 7. Remove carbon deposits from the EGR valve or replace the EGR valve.
I usually pay attention to fuel efficiency when driving, and if the idle speed remains at 1000 RPM after the engine warms up, it's definitely not right. Common causes include carbon buildup in the throttle body, which blocks airflow and prevents the ECU from adjusting the idle speed properly. Another possibility is a faulty coolant temperature sensor, which may falsely report low temperatures, causing the engine to run conservatively. A quick check of the air filter to see if it's clean—replacing a dirty one can help. If there's no improvement, the idle control valve might be stuck and need cleaning or replacement. I recommend keeping an eye on these components during regular maintenance to avoid costly repairs later. If you decide to clean them yourself, use a dedicated spray for a cost-effective and hassle-free solution, but be careful not to force anything and risk damaging the car.
I've driven many cars and seen plenty of idle speed issues. If it stubbornly stays at 1000 RPM after warming up, 90% of the time it's a carbon buildup problem. When the throttle body gets dirty from prolonged use, restricted airflow causes the ECU to maintain higher RPMs. It could also be a vacuum hose leak, like a slow leak in an old tire affecting the system. Sometimes faulty sensors like the intake air temperature sensor can cause this too. My repair experience tells me to start by cleaning the throttle body - that solves most cases. If that doesn't work, check the related circuits. Developing a habit of regular cleaning can prevent problems - don't underestimate these carbon deposits.
