What causes a sudden drop in idle speed?

2 Answers
MarcusDella
07/28/25 8:16pm
The reasons for a sudden drop in idle speed are as follows: 1. Low car battery voltage: Specific detection method: Use a multimeter voltage range to test the battery voltage. If it is below 10V, replacement is recommended. If it is around 11V, it can be used temporarily but prepare for replacement. Above 12V is acceptable. 2. Check if it is caused by carbon deposits: If the vehicle has traveled about 20,000 KM, focus on inspecting and cleaning the throttle body. 3. Inspect and test the spark plugs: Replace them promptly if any issues are found. 4. Incorrect commands issued: The control unit receives incorrect signals and issues wrong commands, leading to inaccurate idle air intake control and abnormal engine combustion. 5. Inaccurate control: Faulty idle air actuators result in inaccurate idle air control.
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Vincent
08/12/25 1:04am
Oh man, I totally get what you're talking about! My old ride had the exact same issue last month. The idle speed suddenly dropped and it almost stalled at a red light. Turned out there was a tiny crack in the intake pipe behind the throttle body - that air leak was basically choking the engine. The mechanic told me these old rubber tubes become brittle after 7-8 years and crack easily. He also suggested checking the spark plugs, saying worn electrodes could cause rough idling too. Ended up spending around 200 bucks replacing the tube and cleaning that layer of black gunk off the throttle plate. Now the throttle response is buttery smooth!
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