High idle at warm

[DeS]

Hello Guys,

I have a little issue since I've done RS2 setup on my 3B Coupe.

After solving problem with N75 conections and geting rid of any leaks car is running well. 1,9 boost, none smoking etc, very nice performance, but..

while warming up everything's fine, idle stands still little over 1000 rpm, but when car is warmed idle starts sticking on 1100 rpms, sometimes on 1200 rpms. After restarting it holds +/-900 rpms, but after giving some revs it hold again too high.

I've checked ISV and TPS connector for good contact and cleaned it up with brush. Also checked TPS with DMM, but I don't if faulty TPS can hold higher revs. PRJ wrote that it only give a boost graph for ECU.

Maybe dirty ISV?

Please give some advice for 1100-1200 idle revs
Cheers,
Pawel

[UrS4boy]

N71 ISV info and Vacuum Line Info

Click on the link below and then on the N71 ISV label live link (all the labels are live for future reference). It could be a dirty ISV or maybe an air leak.

http://members.shaw.ca/speedtek/UrS%20Engine%20Bay%20Device%20Map.html

[A80Avant]

Also check to see that your throttle valve is fully closed and clicks when you are not pressing the accelerator. Finally check the hoses that are connected to the isv

[DeS]

Today I did some checking. I've cleaned up ISV with petrol - it was dirty as hell, but it didn't change the situation. I also changed TPS with another one, but it still don't behave like usual. Its all ok when cold and when restarting at warm, but only after small reving (kicking throtle) it holds on 1000-1200 revs.

Hoses are good, no leaks - car's runing well.


I think ECU is sees some fault and revs up for some reason.

[RustyNut]

Mine is the same. Not sure what it is but as you say the car runs perfect. Confused.

[twoqu]

Do you have Vag Com. If so check for fault codes and the use the 10 measuring blocks to see what is out of specification.
The Workshop Motronic manual for the 3B implies that 1100-1200 rpm idle is limp home. I believe that this represents the ISV rest position (i.e. without power) But I am not sure whether you could just disconnect the ISV electrically and prove this. You will get a fault code if you do that so you would need to unpower the ecu by removing the fuse to get rid of any codes stored or reset via Vag Com.

[DeS]

I think there everything fine with electrics. None ECU faults, they show only when I disconect plugs from ISV or TPS (or any other). When i disconnect ISV plug, revs are getting much lower - thats normal I think.

Another thing is, when I disconnect MAF plug engine stops and its hard to start it (rich mixture). I think that didn't happen before upgrades.

[twoqu]

Well the measuring blocks might give you a clue as to whats happening if you watch them during the transition.
It might be the Motronic coolant sensor not giving the correct temperature (again you can compare this in the measuring block). If the fan runs then the engine is at 90+ degrees, see what temp the Vag com says at the same time.
Out of interest what SW are you running? Is it for 4bar FPR?

[UrS4boy]

Following Robin's lead:

ISV info: http://forums.quattroworld.com/s4s6/msgs/21853.phtml

MAF info: http://forums.quattroworld.com/s4s6/msgs/20442.phtml

G62 Coolant temp info: http://forums.quattroworld.com/s4s6/msgs/20985.phtml

Idle switch info: http://forums.quattroworld.com/s4s6/msgs/20405.phtml

All taken from the hot linked labels here: http://members.shaw.ca/speedtek/UrS%...ice%20Map.html

[nip]

mine is running high at idle now, about a month a go it was ready to stall I cleaned the throttle body even the spring, ever since that it revs about 1100 on warm idle, I boost checked it no leaks, vagcommed it at richys (rj scotty), I cant remember how many codes I had I think it was everything I had to unplug to clean, the only thing I have noticed is that the fpr seal has a small slice out of it I cant see that making a difference but not sure.
Ive replaced the fuel filter /fuel pump, it also has a slight misfire on idle and at low speed seems like its hold back when u press the accelerator it feels like its either on or off (ps sorry to fog your thread Des)

[DeS]

Ok, so I did diagnostic and this is how it looks.


Observations:

- coolant temprature - at 221-223 fan is starting to blow for maybe 5-8 seconds;
- engine load too high - on picture its 24, but usualy shows 25-26 - so its out of range;
- engine speed's too high - we know that
- both Lambdas sticks on 128 and never moves - ???
- ignition timing mostly at 36-37

SW is a MTM named RS2@3B high boost chipset, I'm runing with Bosch Green 968(440@3bar) injectors with standard 3B - 3bar FPR.

[UrS4boy]

- both Lambdas sticks on 128 and never moves - ???

I think that Value 128 corresponds to no adjustment, which is the default.

[A80Avant]

Check the coolant temp sensor at the back of the head. That could also be the issue. I have had that in the past with motronic

[DeS]

I think that Value 128 corresponds to no adjustment, which is the default.

So, you suggest its stucked and not working properly? Need to be replaced?

Check the coolant temp sensor at the back of the head. That could also be the issue. I have had that in the past with motronic

It's OE Bosch, changed not so long ago.

[twoqu]

Well 215 would be 105 degrees and if the fan comes on at over 220 that would make it over 110 degrees. Usually tthe car should run at 88-90 degrees. So either it running very hot or there is indeed an issue with the temperature sensor for the Motronic. Thats the one in the cylinder head not the MFTS.
The static 128 is usually down to not enough fuel.
As you say some are out due to the idle speed but the others are near the bottom of the range which I guess is the maximum it can control in one direction.
So I would suggest testing the coolant sensor before changing it.