Strange idle connected exhaust vibration

[twoqu]

One connection for the coolant sensor is at pin 30 (earth), the other is at pin 45. The sender provides a resistance dependent upon temperature back down to pin 45 which the ecu reads to determine the temp. Therefore I think we should be able to read whatever resistance the temperature senser is sending by testing the resistance between those two pins in the connector. If the car is cold now, it should be nearer 2800 ohms thats 2.8K ohms not 200.
So thats approx 2800 ohms at 20 degrees C or 200 ohms at 100 degrees C. You will need to set the MM so that it can read above 2000 ohms.

[newsh]

Sorry I am confused now.DO you mean probe between pin 30 and pin 45,with the MM at the 200k ohms setting and the ignition turned of,then there is nothing.
If there should be a connection of some sort Between PIn 45 and pin 30 on ECU ,it is not there,so is this the reason for my problem do you think

Yes, you should see the same resistance as you saw on the spare sensor when you were trying it off the car. All you're doing is adding the connector and the wires to the ecu into the circuit.

If you can't get a reading then this is definitely a problem that needs fixing and as you can't get a reading with the spare sensor then it seems like its the sensor connector!

[220bhp]

The connector is not good and needs replacing,along with the sensor itself.
It may or not be the problem, but unless I replace both,I will never be sure.
The thing that buggs me is what ever I do THe idle still hunts at 1450,hot or cold.
Every thing points to the ISV and the control to it.The other causes for this condition are as pointed out earlier in this thread.Ie vacumme leak.TPS clicking to early. Plus leak between Maf and throttle body.
I have both replaced and tested the vacunne lines.And I have done a boost leak test more than once.
The only other thing,Apart from the TPS opening to early, is the wastegate bolts may be not tight enough.I have checked all these things,But I cannot be sure with my limited knowlege, wether I have done these test right,But I asume I

[newsh]

If the temp sensor is not working then the ECU thinks the engine is cold and tries to raise the idle speed via the ISV.

[220bhp]

I agree John. but I cannot understand why the idle still hunts,when its hot or cold,even with varios sensors dissconnected.

[twoqu]

Lou,
Similiar condition solved by coolant sensor replacement?

http://www.s2forum.com/forum/showthread.php?p=655792#post655792

[driftin jo]

I agree John. but I cannot understand why the idle still hunts,when its hot or cold,even with varios sensors dissconnected.

Have you done a compression test ? Low compression on one cylinder could cause this,
especially if the cause of the low compression is an inlet valve not sealing.

[newsh]

I agree John. but I cannot understand why the idle still hunts,when its hot or cold,even with varios sensors dissconnected.

When I described your symptoms to Pete he immediately said he thought it would be the white G62 sensor. He said its quite a common problem.

[220bhp]

When I described your symptoms to Pete he immediately said he thought it would be the white G62 sensor. He said its quite a common problem.

I have one on order from pete at Quattro corner,should arrive today.
I am going to replace the connector as well.
The only thing that I am concerned about is the this connectivity between pins 30 and 45 on the ecu connector.If it should be there,it isn't.

[twoqu]

If you cannot get the resistance of the sensor between those two ecu pins in the connector then either there is a problem with one or other wire, or the sensor is open circuit.
To check the wiring, measure for continuity from the sensor connection back to the pin in the connector. If the wires are ok, that only leaves the sensor.
Let assume that a good sensor has a reistance of 2800 ohms at 20C. Then as John as said, all we are doing is adding two lengths of wire to the sensor. If the wires have continuity they have 0 ohms resistance. So when we measure from one wire to the other through the sensor we should have a resistance of 0+2800+0=2800!
Just make sure that your MM is set to an appropriate range to measure over 2000 ohms.

[220bhp]

Robin , So are you saying that the connection between PINS 30 and 45 on the ecu will
only occure if a good sensor is connected to complete the circuit.
I have continuity on both wires to the ecu,and 5 volts on one.

[twoqu]

Yep!
Think of the sensor as a resistor connected between the two pins. If one end becomes disconnected then the circuit is broken. In that case you would get no resistance. You would still get continuity down the wires if tested individually.
As I understand it the ecu sends out a reference voltage to the sensor. The resistance of the sensor due to the temperature alters the voltage and the ecu calculates the temperature. It would seem that this voltage is 5V from your measurement, like most of the other sensors.
Check out the post I refered to above. Looks like another sucess!

[newsh]

Yes this is correct. Consider the spare sensor, you measured it's resistance at 1990 ish Ohms when cold and 500 Ohms? when hot..
If you plug it into the loom and take the multimeter to the ECU end then the measurement should be the same, depending on temperature of the sensor.

Also, don't forget that the circuit can be broken if the mating surface of the pins are corroded in the connector at the sensor end of the wires.

[220bhp]

Fitted the new temperature sensor, and a new connector.Cleared the ecu and let it run up to temperature.Idle still 1050.Took nit for a drive and it is definitely better than it was,but it still hunts at 1450 revs and the drone is still there at 2000,but no where near as bad. 1.4 boost at one point,no popping or missing,but then it dropped to 1bar and would not go past that.
Strange thing happened when it was warming up,I started it without touching the accelerator,and just left it to warm up,after a minute or so the revs just shot up on there own,never done that before,very odd.
I guess its back to the drawing board

[newsh]

Did you crimp new pins on as well or just the connector shell?

Can you do the resistance test again between pins 30 and 45 of the ECU connector up to the sensor just to be sure we have a circuit now?