High idle - hot weather

[Edmundo]

HI,

 

I have Superb MK III 2.0 TDI 150 HP. I've got it in February, traveled 11000 miles so far.

 

In my country weather temperature is very high since beginning of May, last 20 days over 30 C (86 F). When weather is like that, AC is on, engine in idle constantly works on 1000 rpm. It is more noisy and burns more diesel. It would not go back to 750 rpm unless I turn off AC and slightly press throttle pedal. After turning on AC and pressing throttle pedal it goes back to 1000 rpm.

In the morning and in the evening, when it is cooler, it works on 750 rpm.

 

Car was in service shop, no error found, no solution given. It is not DPF regeneration.

 

What could be reason for this? I guess this is not normal working mode.

 

Thank you.

[skidpan]

When the A/C is on there is additional load on the engine. When the weather is hot there is additional load on the A/C. So the engine has to work harder and to avoid stalling it increases the idle speed.

 

Had similar on a few cars, some did not even need the weather to be terribly hot. On one Micra as the A/C cycled on and off at a set of lights the idle speed would be up and down like a brides night dress.

 

Sound perfectly normal to me

[Edmundo]

Yes, that is first thing that crossed my mind. But than I talked with some other MK III owners in my country, their cars work on 750 rpm. 

 

Also, we are talking about 2.0 150 HP, there should be enough power for A/C to work without additional rpm. 

 

What is experience of other owners on this forum? I guess I am not the only one who drives it in hot weather. 

[FelisBengalensis]

It will also depend on what ancillaries are running and the charge state of the battery.  You need higher idle speeds for the alternator as well.  Add in cooling fans and it all generates engine load.

[silver1011]

My 2011 MkII does it too so it isn't new.

[Superb170]

Sounds normal to me as well and is how mine usually behaves this time of year.  There is a lot of extra electrical load trying to keep the car cool

[Speedman]

My 190 DSG does exactly the same when the air con is working hard on hotter days so guessing it is normal although I have not had a car that does this before.

[Edmundo]

Okay, thank you, guys. I guess I am just expecting to much

[Enobar]

I can't really remember noticing much difference in idle speed when it's hot, though it wouldn't  really surprise me terribly either.  30° though is a pretty mild summers day here though... may not even have the a/c running ;-p lol.

Edited 2 July, 2017 by Enobar