No matter how long I drive in city traffic (could be over 30 mins) the engine never warms up to optimum, which means it idles at 1200. If I take it for a motorway drive it will warm up fine. My Glasgow Lexus dealer refuses to even look at it....says that is "normal". Anyone has same experience?

most diesels i have owned are like that

same with mine, however I have a "power heat" button which starts the eberspacher heater and this helps a lot.

Blame it on the Scottish Climate, got the same problem.... Out of curiosity do you the problem of the engine idle speed going up to 1200 in standing traffic...?

Yea during warm-up it idles at 1200. If you put off the climate control (not just aircon) it will idle at 800 nicely. Once fully warmed up will idle at 800 all the time whether the climate control is on or off. Lexus Glasgow says that is perfectly normal. But it is a pain though! I often put off the climate control while sitting at traffic jams, but then it gets too cold....wonder how a manufacturer like Lexus cannot get something simple like this right! There are various forum topics on this throughout this site.

What's the basis for your belief that they don't get it right - or indeed that it is simple?

It is part of the basic operating mode of diesel engines that they are slow to warm up.

In a petrol engine running at low speed, the air supply is throttled so that the right quantity of air/petrol mixture goes into the cylinder. The system is designed to keep the mixture close to the stoichiometric ratio, otherwise it becomes difficult to ignite the mixture. Power is regulated by varying the volume of the air/fuel mixture induced at each stroke. So, as the power requirement reduces and engine speed decreases, so does the amount of cold air drawn into the engine on each stroke.

In a diesel engine each intake stroke takes in a full cylinder of (cold?) air and then a small amount of fuel is injected. Power is regulated by varying the air/fuel ratio and the air volume per stroke remains more-or-less constant. The diesel approach is more efficient but because much more air passes through the system on each stroke, the cylinder block stays cooler.

The amount of power required to keep the engine ticking over varies considerably with the temperature of the engine. Much of the variation is down to the change in the level of "pumping" losses as the viscosity of the lubricating oil changes. So, essentially, a cold engine uses more power than a warm one, just to keep itself turning over.

Finally, aircon systems consume significant amounts of power, in a typical car it may be around 2 horse power (1500 watts).

If you put all this lot together, it is hardly surprising that tickover speed does not remain constant. Much of what I have said has been simplified, but I think there is enough still there to make the point that it is not a simple matter.

you explained whole thing perfectly and thank you for that, but here is one point where I disagree. It is true that the A/C cooling takmes 2-5hp but when you turn off the A/C button, the whole aircondition consumption constits of the electricity for fan and couple of sensors. And it still needs to rev 1200.

If I turn of the whole climate system, but I turn on both seat heaters, rear window heater and the wiper heater, the electricity consumption will be surely higher than has the climate system without the A/C however the engine has no problem at all to rev just 800.

Personally, I am not bothered of 1200rpm when idling, because there is less vibrations when cold and I am happy with my consuption... It is just another thing where lexus is not that smart, as it should be.

Well explained Sagitar, and also well countered Matus.

Still doesn't really explain why:

1. The idling speed will not drop to 800 when the aircon only (the aircon compressor) is turned off but will do so when the whole climate control is turned off. I would have thought if the aircon compressor is taking up so much power, turning it off would do the trick, without having to turn off the whole climate control.
2. My previous BMW 525d heats up a lot faster, and never idles at a high speed when warming up. My use of the word "simple" is obviously symbolic. I agree that nothing is "simple" when it comes to technology, but come on, if other manufacturers can do it surely Lexus can too!

My experience of diesels is limited, but I do know that in my work where I often get driven in a Skoda Octavia 4x4 diesel the engine heats up quickly, and idles at under 1000 rpm regardless of engine temperature.

Some diesel cars have "preheater", usully eberspecher or webasto, and this runs automatically from certain temperatures and helps to heat up the engine. I have it too, although not automatic, but as I see, UK IS's don't have it...bloody savings.

doesnt it keep up the revs to get the car warmed up when the heating is on? switcing the heating off will reduce the revs to 800. When it reaches optimum temprature then the revs always stay at 800 when idle. I don't think its anything to do with the aircon.

It is something that is unique to the 220D, I have a Nissan, also with 2.2 diesel no matter what the temp never idles above 800 rpm. Went from Hamilton to Glasgow (14 miles) and the the engine was still running at 1200 rpm when I hit the city centre, switch off the heating and it droped to 800, switch it on and it goes back to 1200... and you wonder why the fuel consumption is poor for a diesel.... Well IMHO here is one reason....

Oh and by the way no matter how hard the nissan is driven never goes below 42mpg and it heats up a lot quicker than the Lexus

Am I talking Rollex or is the engine all Aluminium? If so, does that make a difference, as Aluminium has to run cooler????

Just looking to find an excuse to defend the marque...


I too haven't actually had a diesel where I have noticed this, but have done on the Lex....

I am trying my best to defend lexus as well, especially against colleagues who have A4's & BM's.... There is a noticible difference in the time it takes the Lexus to reach operating temp against others... at least the heated seats help

i think the revs drop as soon as the car starts to roll or you press the gas pedal.. so that shouldnt affect the MPG.

its purely a feature to get the car wramed up asap.. for instance the car is idle in the driveway you can get the car warmed up quicker. Soon as you blip the gas pedal it drops down to 800 then rises back to 1200