Help with idle.

[Anders229]

Hi everyone!

I have a problem with my van, 2,1 MV, its revving up at idle after approx one-two minutes when it´s a little warm, don´t matter if i shut it off, and start again, it has too cool down again to have a stable idle that minute.. I have tried to change LMM, idle control valve, disconnect lambda and searched for leaks, whats next? It doesn't rev up if I disconnect the idle control valve, but that won't solve the problem...

Pleeeease help me!

[Anders229]

Oh, and I have changed the blue tempsensor too!

[937carrera]

When the engine is fully warm does the idle settle down or is it also high then ?

[Anders229]

When the engine is fully warm does the idle settle down or is it also high then ?

No it is the same, I guess anyway, I tested a couple of times with the idle control valve unplugged and drove around a bit, but it is still revving high when I connect it again.

[937carrera]

Take a look at this thread

https://club8090.co.uk/forum/viewtopic.php?f=37&t=168680

The idle control valve / aux air regulator allows extrra air in when the engine is cold. When hot it should not be doing anything. The high idle indcates that too much air is getting into the engine, and other than through the correct route. In this case I suspect it is getting past the throttle valve bushings, it's a common problem with these systems

There are useful additional download links in that thread

[Anders229]

Thank you! I will have a second look at the throttle body, I know I checked that micro switch and felt for some movement in the bushings and it seemed ok then.

But, when I disconnect the ICV, if it was the throttle body, shouldn’t it rev anyway then? The engine runs without the ICV, but not good! But the idle stays ok!

I’m just guessing here, but if some temp sensor tells the ecu to choke the engine when I start it cold, and as soon it’s warmer then like 10 degrees the ecu switches over to something else and thats when I have a problem?

[937carrera]

Sorry, I only posted half a reply, doing forum posts while doing something else and I ignored not only your answer to my previous question but my own thoughts.

Yes, I agree with you. It would appear a false signal is causing the ICV to increase the idle by allowing air through when the engine is up to temperature. The fact that it doesn't run as well when the ICV is disconnected also seems to signify that the engine is on a cold engine map (i.e too rich for normal running)

I don't know the details of the MV that well but a quick look at the wiring diagram seems to indicate that there is just the one temperature sensor, and that provides a resistance value to both the ECU and the ICV. Can you ascertain the expected values for the temperature sensor and make sure that is the resistance being obtained at the sensor itself, and back at the ECU/ICV. I would also suggest puting a suitable value resistor in circuit instead of the temperature sensor and see how that affects the running and idle. It might be a good ICV and temp sender, but grotty cable inbetween them.

If you want wiring diagrams go here http://syncrosport.com/info/wiring/

If you have the idle stabilisation box on the left hand side of the engine compartment, unplug the two connectors and connect them together to eliminate that from the equation

[Anders229]

I know the feeling! Thanks anyway for your time!

I will investigate all of that you have mentioned.

Me and the kids drove a couple of laps around the house today, and it didn’t start to mess with the idle until it was really hot today? That was strange, but it is still kind of weak and has no bottom end, put it i G gear to be able to climb a little hill...

[937carrera]

http://archive.club8090.co.uk/viewtopic.php?f=2&t=19191

The post from Harry Mann has some test values for the temp sender for you.

Note he also suggests it could be simply a deterioration in the wiring, or grotty cable as I called it........ as you can see higher resistance indicates a lower temperature which is very much in line with your symptoms