Unlike starting the car in the afternoon, after you've already started it at another time of the day. I understand that the higher RPM can be because of the temperature, however on hot days it's still the same.

Are there any other reasons besides temperature?

I have a 1.5 Manual Honda Mobilio.

  • Can you please specify the year, make, model, and engine size of your vehicle? Feb 19 '16 at 2:18
  • Modern fuel-injected vehicles have several different idle speeds that depend on the temperature of the motor, what gear you are in, and other variables. When you start the car in the morning it has several systems that are working to get the engine up to operating temperature as quickly as possible. The ECM will increase the idle speed when the coolant temperature is below a certain threshold. Feb 19 '16 at 2:26
  • @DavidWinslow I have edited to add details to what car I have. Feb 19 '16 at 2:30
  • you have nothing to worry about ,its normal behave of engine due to difference of out side or ambient temperature .car ECU just injected more fuel for worm up the engine coolant and also the engine to optimum temperature .but if after sometime the engine rpm not drop then you have to check by a technician .And the other things is that if after run the car when you stop your car at a traffic signal then you see engine RPM fluctuate this fluctuation is problem and its need to check up. Nov 4 '19 at 17:11

All ambient temperatures are below engine operating temperature, so you'll still get "cold engine" behavior on a hot day unless you drove the car recently.

Every car is different and will have a different cold start process, but coolant temperature is the dominant factor in whether this behavior triggers on the cars I'm familiar with.


you would be surprised how hot the engine can be and the ECU will still raise the idle. for example on my 1999 Nissan Almera 1.6 liter the computer will raise the idle until the engine reaches 80 degrees Celsius. I have verified this with a scan tool.

  • My 2012 Civic SI shows a low temp light until the coolant temp reaches 125 degrees F.
    – Tim Nevins
    Nov 5 '19 at 15:04

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