Higher cold start RPM levels in NA petrol engines

I have noticed recently that on most days, when the engine starts, it runs at around 1100 rpm and a warm engine runs at 600-700rpm. This is particularly true of cold starts is in the morning.

BHPian gopaneel recently shared this with other enthusiasts.

In all fuel injected cars I have used in the past, I have observed that with cold starts, the engine runs at a higher rpm than normal idling speed and once the engine warms up, it slows to normal idling rpm. I thought it was the same with my Glanza, now about 7 months old. As I remember, while starting, it used to idle at around 1400 rpm and then settle to a lower rpm. However, I have noticed recently that on most days, when the engine starts, it runs at around 1100 rpm and a warm engine runs at 600-700rpm. This is particularly true of cold starts is in the morning. On a few occasions, rpm goes to 1500 in cold start till the engine warms up and strangely I have observed this during afternoon/evening. I'm confused if I was initially imagining that the cold start rpm was always 1400 or that was actually the case. Could there be a reason for different cold start rpm i.e. 1100 vs 1400? Other than this there are no other issues, in that, the engine runs smooth after all cold starts unlike my carburettor(ed) bike which seems to gasp for fuel/air until it warms up. Has anybody else observed different cold start rpm values?

Here's what BHPian a4anurag had to say on the matter:

Yes, I have observed the difference in our Ertiga 1.5L Petrol engine too. Nothing alarming anyway so never worried about it.

MAF sensor sends all the necessary readings and the ECU decides what is to be done IMO. Don't think it is set fixed at an RPM for cold starts.

Here's what BHPian scorpian had to say on the matter:

Depending on inputs of ambient air temperature etc., the MAF sends signal to ecu which controls the idle at cold start.

You could disconnect the negative battery terminal, pump the brake pedal to discharge any residual current and connect battery terminal after a gap of 30 mins. Just for knowledge sake you could try it, wont do your car any harm.

Here's what BHPian Indian2003 had to say on the matter:

It all depends on the temperature. My car with a 5 cylinder engine revs at 900 RPM in the summer months at start and drops down to 850.

In the winter, in sub zero temperatures, it revs at about 950 RPM at start for a few seconds before dropping to 850 RPM, but then I drive as soon as the engine is started. Your car sounds normal to me as a cold start in India is summer temperatures here where I live.

The manifold temp sensor should regulate the engine speeds in the cold.

I would say that 1400 RPM at start is way too high.

Here's what BHPian Researcher had to say on the matter:

As others have pointed out, you have no reason to worry if it goes back to 600-700rpm after a few seconds. In our Baleno, it stays the same for about a minute before settling down. It takes slightly longer in my SX4, which I am guessing is probably due to thicker recommended 5W-30 oil vs 0W-20 in Baleno. From what I have observed and others have mentioned, it varies due to any changes in the following:

• Ambient temperature
• Altitude
• Operation of air conditioner (changing idle if switching on the AC immediately after ignition)

Since its only 7 months old, you need not worry as it is still under warranty for quite sometime but please mention this to your authorized service center next time you visit so that it is on the records.

Here's what GTO had to say on the matter:

I have always noticed this with NA petrol engines, but weirdly, never with diesels. Their cold-start & warmed-up RPM remains more or less the same. Why is that? Or is it a turbo thing?

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