[gopaneel]

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 1400rpm and then settle to a lower rpm. However, I have noticed recently that on most days, when the engine starts, it runs at around 1100rpm 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?

[lxskllr]

My 2 cents.

On my Baleno, the cold start rpm is usually around 1400-1500rpm, and post idling for roughly a minute it settles between 600-700rpm. I haven't observed any variation in the cold start rpm. Will report back if it's any different at different times of the day.

[a4anurag]

Originally Posted by gopaneel

Could there be a reason for different cold start rpm i.e. 1100 vs 1400?

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.

[scorpian]

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.

Regards,
Manoj.

[Indian2003]

Originally Posted by gopaneel

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.

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.

[Researcher]

Originally Posted by gopaneel

Could there be a reason for different cold start rpm i.e. 1100 vs 1400?

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:

1. Ambient temperature
2. Altitude
3. 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.

[toiingg]

This was the case with my 2001 esteem as well. Cold starts would put the RPM at 1200-1400, which would then come down to 800 odd after a couple of mins. Pretty normal.

[aaggoswami]

This is absolutely normal. I had K12M equipped Swift for close to 5 years and I sold it with around 43,000 kms. on odo. Very cold starts meant engine idling at around 1500 rpm. for half a minute or so, rarely more than that. I usually would wait for this to happen before I start driving in winters. Post that till engine comes to operating temperature idling was at 1000-1100 rpm and then 700 rpm once engine has warmed up. In summers the idling never went above 1000-1100 rpm. You will also observe slightly more vibrations when engine is idling at 1500 rpm as its a cold engine. It hovered at 1400-1500 rpm. Infact, many a times, if I engaged 1st gear with engine at 1400-1500 rpm idle, move barley a foot and then again brought the car bad to a standstill the idling 1400-1500 rpm. It all depends upon ambient air temperature.

Baleno 1.6 also had this, but not 1500 rpm. There is nothing wrong with the machine, enjoy munching many more safe miles.

[gopaneel]

Thank you all for your inputs. Looks like there's nothing to worry about. But will mention in the next service as suggested by Researcher.

[audioholic]

As emission norms get tighter and manufacturers make engines more efficient with thinner oil and lesser friction, the need to run at higher RPM when cold also is reduced. Hence, the newer the engine, sooner it will settle to its warm idling speed compared to older petrol engines. It's completely normal as long as you don't face any stalling issues or such.

[GTO]

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?

[Kosfactor]

Originally Posted by GTO

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?

Petrol is like the good old Choke which your Premier must have had, more fuel to keep the cold engine running without stalling. Nowadays the ECU has taken over to maintain the driveability right from the word Go, so there is more than just more fuel and air going on in there, emissions , need to reach a warm temp for the engine to run more efficiently sooner etc.

Diesel , on a cool morning you would notice a CRDI engine runs a bit faster at cold start, this is done to warm up (ever so slightly) soon as well as to keep the vibrations down, when it gets really cold there is very little even the ECU can do on that department though, it will run like an old tractor for a minute. If you are driving immediately after cold start the warm up is cancelled.

[gopaneel]

Originally Posted by GTO

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?

I think the earlier diesel engines had a glow plug to help with cold start. I am not sure if the newer ones do. In petrols I believe cold engines run a richer mixture. The diesels probably don't do that because of the glow plug. Just a guess. I am sure there are experts here who can clarify

Regarding my car, I know the fuel injected petrols run at higher rpm on cold start. In case my initial post was not clear, it's only recently that I noticed that there seems to be 2 levels of cold start rpm, sometimes it's 1100 and sometimes close to 1500. The usual idle is around 650. I've only noticed a single high rpm in cars I've used earlier and also in the Glanza until now.

[AirbusCapt]

Interesting! On my Versys650 the bike idles at 2000rpm for half a min, 1500rpm for a min and then drops to normal idle of about 1000rpm. This is irrespective of ambient temperature. This behaviour is documented in the manual and it is advised not to ride until the rpm drops to 1000rpm.

[DevilzzzzOwn]

Originally Posted by GTO

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?

Actually, in my first hand experience, my XUV 3OO Diesel revs at close to 1K rpm for around 30 seconds. While it is doing that, I use the time to buckle up, connect the Android Auto (wired), check my mirrors. After 30 seconds or so, the engine settles down at around 800 rpm and I move away.

And this is in Pune, hilly regions with ambient temps in the range of 15 (early mornings) to 30 (during day).

I have NEVER observed that my diesel DOES NOT rev harder at the start. And I don't touch the A pedal during the entire process, so I am sure turbo has nothing to do it. Infact, I am so paranoid about cold starts and turbo that for the first 2 kms or so, until I hit the main highway, I keep on constantly upshifting at the earliest opportunity. Being an AMT, it means driving in the Manual mode which is jerky for the first 5 minutes.
But once I get 2 bars on the temp gauge, everything smoothes out, I am settled, engine is settled, gearbox is upto the temperature and then I slot it in the Auto mode.

Definitely OT, but since we are talking about temps, did we reach a conclusion on how long to idle a turbo diesel AFTER stopping? I know there are multiple threads with the discussions but they don't seem to reach a conclusion ever. Of course, it's natural that everyone is different. But I follow the 10 second rule. Park the car with no throttle inputs, stop the music, unbuckle and then shut off the engine. Thoughts?

Also, out of curiosity, another one. In the past, when I used to observe bus and truck drivers, on stopping their vehicles at a designated place, they would disengage gear and then rev the engine twice or thrice. And not just quick short blips. I am talking long 1 second blips, enough to make the exhaust bellow thick clouds of black smoke. What was that about?