Adjusting Engine Idle Speed - 101

[Turbo Steve]

1999.5 and later A-4 TDI's have engine idle speeds varying from 882 - 945 RPM's and a VAG COM or VW Scan Tool can be used to raise or lower engine revolutions in the following manner:

Example (VAG COM)

1. Click on "Select"

2. Next, on "01 - Engine"

3. Then "Adaptation"

4. Under "Channel Number," scroll to Group 02.

5. Current Idle Speed will be displayed in the upper left-hand corner.

6. Under Channel Number, is a block with 5 digits in it, representing a numeric value of ECU code.

7. Enter your new desired value in place of the existing number or use the up and down arrows to change the existing digits.

8. Minimum value accepted is 32743, which equates to 882 RPM's.

9. Maximum value is 32803 which equals 945 RPM's.

10. Once a new value is entered, click on "Test" to see how this changes the Idle Speed.

11. Finally, don't forget to "Save" the new configuration before "Exiting."

Note: The ECU will only accept digits within the 32743 - 32803 range and whenever a value is entered outside of those digits and tested, the VAG COM will automatically adjust your selection to the highest or lowest acceptable value.

Saving the configuration is the same (whether or not you tested it) and out of range numerical values will be changed to the closest 32743 or 32803 figure.

Thanks to TDI Ray for pointing me in the right direction - Just remember "Engine Adaptation" as a keyword.

[ January 02, 2002: Message edited by: Turbo Steve ]</p>

 

[Turbo Steve]

For those of you wondering how MPG is affected by raising or lower the idle, VAG COM's Group 015 Block 3 displayed Fuel Consumption as .4 Liters Per Hour with the engine idling at 882 and 945 RPM's, so any difference is definitely negligible.

 

[SkyPup]

That's great!

Thanks for the good info.

 

[Turbo Steve]

Some advantages of raising the idle speed might be:

* Slightly more load on the engine.

* Increased load equals faster warmup times.

* Helps engine maintain heat during the winter and not cooloff so much when idling in the cold.

* Slightly improved piston ring seal.

* Less blowby contamination into crankcase means slightly cleaner oil.

* Less cylinder wall glazing.

* Higher idle is better for journal and rod bearings.

* Camshaft lobe wear should be reduced a little too.

* Charging System works better at higher speeds, even though generators are better than alternators at idle.

* Load on Power Steering Pump is reduced with higher speed.

* Liability of lugging when taking off is reduced.

* Slightly improved go-pedal responsiveness.

* Slightly higher oil pressure maybe 1 - 1/2 PSI, every little bit helps.

* Increased circulation of oil provides a better cooldown before shutdown.

* If ECU is not displaying an increase in "Fuel Consumption" (Group 015, Block 3) and staying at .4L/H for 882 & 945 RPM's respectively, raising the idle a little higher to 945 doesn't come with a noticeable fuel penalty.

Besides, Ric, who's going to complain if it takes $13.02 to fillup instead of $12.99?

[ January 02, 2002: Message edited by: Turbo Steve ]</p>

 

[Sooty]

Eric, before you get too excited it only applies to OBD II ECU’s or in other words none European cars.
The info’s been on Uwe’s egroups section.

 

[VelvetFoot]

What is the spec for the idle from the factory?

This would be cool. I have always felt that idle was too high.

 

[Turbo Steve]

Velvet:

903 appears to be the most common idle speed from the factory and perhaps this is also their in-house standard to shoot for as well.

A-4 ECU's seem to only accept an idle speed between 882 and 945 RPM's.

 

[VelvetFoot]

I tried to do this with vwtool but the program bombed out with an 'Overflow' error. I guess I'll go to the egroups. Do you have to log in first?

 

[Eric Maurier]

Yo, great info! Still have to see if it works, but I'd be interested in knowing what your source is. I don't remember having seen that in the bentley nor in VW's official injection manual which I have in paper edition.
Thanks a lot for sharing anyway!

 

[Eric Maurier]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by Sooty:
Eric, before you get too excited it only applies to OBD II ECU’s or in other words none European cars.
The info’s been on Uwe’s egroups section.<hr></blockquote>

definitely works on mine. No login needed, the original value is 32768, raised it to 32803 and the rpms now are 945 instead of 903. I think now, I should have tried a higher value, maybe it would have worked on mine. We'll see this WE.
But you may not be wrong, after all. Given their price, those Skodas can't be european nor do they come from anywhere in the world: they must be from Mars

Can't believe I missed that on the VAG-COM list. For once, it wasn't about a throttle body adaptation or an oxygen sensor

and I didn't see it. What a pity

ECU #: 038 906 012 H. Should work on all the cars that have the same number.

Karl: when you manage to raise the idle, I'd be interested in knowing if the oil pressure changes much. TIA

[ January 03, 2002: Message edited by: Eric Maurier ]</p>

 

[VelvetFoot]

Eric, I am thinking of dropping the idle speed. I did find this topic on the vag-com egroups. I have discontinued getting the emails for a while, so maybe I should check in once in a while. I found out today that I'll be getting a new laptop at work so it's Vag-Com next!

Do you think from dropping it from 903 to 882 will have any bad effects? (Like not enough oil pressure at warm temp? Hard to believe, for 20 rpm's.)

 

[tongsli]

Steve,

thank you for helping me adjust the idle. It has all but ELIMINATED the slow down shudder. Now, I have to TRY and feel a shudder. It's very, very very faint now.

The new 945 value did the trick. Thanks

Lito

 

[Turbo Steve]

Lito:

You're Welcome!

It's amazing as to the unity experienced when the ECU and Pump work together, instead of the Pump wanting to push more fuel during a slowdown than the ECU prefers.

Raising the idle means the ECU is compromising and NOW happier with the Pump's output at 945 RPM's, but before, the computer expected less fuel than the Pump was adjusted for and software intervention results in shuddering as the Pump and Computer argue back and forth.

 

[Eric Maurier]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by VelvetFoot:


Do you think from dropping it from 903 to 882 will have any bad effects? (Like not enough oil pressure at warm temp? Hard to believe, for 20 rpm's.)<hr></blockquote>

I don't think so. But as I've never had a pressure gauge, I can't tell you for sure. I've raised it hoping to get a little more pressure to the camshaft but I don't think it will be of much use.
On the other side, lowering the idle should get you more mpg especially in city commuting and (maybe?) cool down the turbo faster (less fuel injected-> less heat). But the effect of all this should remain marginal

I'm glad you have a new laptop. Now you will be able to get those multiple groups logged and hopefully show us some wonderful excel graphs

I wanted to congratulate Uwe for cracking the 7-digit pin VW is using in the "Rest of The World". No use for the US/Canada, but a great step for everyone else! Yes, VAG-COM will be able to generate the pin in the next version!

 

[Turbo Steve]

I agree with Eric that raising or lowering the idle speed results in "marginal" gains within the 882 - 945 range, but every little bit helps and the +/- load on the engine is what causes it to heatup or cooldown.

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by Turbo Steve:
For those of you wondering how MPG is affected by raising or lower the idle, VAG COM's Group 015, Block 3 displayed Fuel Consumption as .4 Liters Per Hour with the engine idling at 882 and 945 RPM's, so any difference is definitely negligible.<hr></blockquote>

 

[Harvieux]

Hi Folks, I just got my Vag-com and I take it that this idle adjust will only work on A4's and not B4's or A3's. Is there any way to adjust the idle on A3's or B4's? Thanks and Later!

 

[Sooty]

Apart from trying it yourself I can’t say for definite. When I first saw this trick years ago I tried it without success, somebody at the time told me it was only an option for NA cars due to omissions as it allowed dealers to adjust for bad local fuel, and as such the code was only available in OBD II enabled ECU’s. It’s possible I was fed BS, but it did seem to fit what was happening at the time, if it is true then I believe it should work on a NA A3/B4.

 

[SoTxBill]

quote:

Apart from trying it yourself I can’t say for definite. When I first saw this trick years ago I tried it without success, somebody at the time told me it was only an option for NA cars due to omissions as it allowed dealers to adjust for bad local fuel, and as such the code was only available in OBD II


I doubt it has anything to due with fuel..if the fuel is bad, the ecu sense's rpm and just turns up the pump to get back to the same idle speed..945rpm or whatever its set at...... cetane does not affect the burn time at an idle on a warm engine..

but i suggest it has everything to do with emissions and driveablilty problems (rough idle w a/c comressor on or keeping charging during high loads when at stoplights)... and the lower the idle, the more dirty the engine is.. all engines after 1965 were idled up to clean them up..

and if your in stop and go driving, the idle speed has a great deal to do with mpg.. used to try different settings on my older vw diesels and saw about 2 mpg loss by running 850 vrs 650rpms..

made no difference on highway driving...

650 was the lower limit i found,, 700 to 750 was much better,, but i thing the 900's is for emissions... just my thoughts.. Bill

 

[Cleemaans]

Guys,
I've read several posts already about the 'SHUDDER'-fenomen.
I've got a Golf IV TDI with 110bhp ( european ) with this strange shudder when decreasing speed.
My dealers says that changing the ECU will solve the problem, but that costs a lot.

My question is that changing the idle-speed will solve this problem ?

Thanx

 

[Turbo Steve]

"My question is, [will] ... changing the idle-speed ... solve this problem" (Cleemaans)?

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by Turbo Steve:
Raising the idle means the ECU is compromising and NOW happier with the Pump's output at 945 RPM's, but before, the computer expected less fuel than the Pump was adjusted for and software intervention results in shuddering as the Pump and Computer argue back and forth.<hr></blockquote>

Cleemaans:

If the Fuel Quantity Adjuster within your Injection Pump is set out of spec, raising the idle speed will not be enough to overcome shuddering during low speeds when the ECU expects to see less fuel than the pump is mechanically adjusted for.

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by Turbo Steve:
It's amazing as to the unity experienced when the ECU and Pump work together, instead of the Pump wanting to push more fuel during a slowdown than the ECU prefers.<hr></blockquote>

BTW - What are your readings using VW Scan Tool or VAG COM, after going to Select, 01 - Engine, Measuring Blocks - 08, Group 001, and recording the numerical values in Blocks 2 and 3?

Please post your readings here: http://forums.tdiclub.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=3&t=006790

 

[Cleemaans]

Thanx for the quick reply...
I don't have that VW scan tool available...
therefore I have to go to my local dealer I guess..
I already spent a lot of money there but the problem remains ...
Should I ask them to read out these results ?

Sorry for my poor English...

Greetz...

 

[Sooty]

Update from my previous post, it indeed looks like I was given duff information in the past.
I just tried VAGCOM Alpha 0.81 and I can now adjust my idle – looks like a problem with previous releases of VAGCOM and my 1Z controller.
Having said that I’ve left it at 903rpm since I’ve never had any problems and have got used to the noise that way

 

[Dslbeet]

99 ALH here, I replaced the 2 cover plate gaskets on the injector pump, and now my idle just keeps going up. I have to shut it off to keep it from increasing the idle. Any thoughts on what I did wrong?

 

[BobnOH]

Likely the quantity adjuster is out of position. [this thread is 19 years old]
Try some searches using various keywords to help you get it back in position using this user contributed search engine-
VW TDI Search Engine

 

[Dslbeet]

Thank you. I got it running without increasing rpm, but now the idle is rough. Besides that it’s running great.