S6 AAN idle problem when cold and N71 connected

[doncecone]

Hi guys,

I have the following problem. When cold and I start the engine it dies after 3 seconds. I start it again and it dies after 5. If i push the accelerator pedal a bit it doesn't die. If i disconnect the ISV valve it starts and hold very low rpm but doesn't dies. Once warm, car runns fine both with or without ISV. No faults with VAG-COM. What could be causing it to dies with connected N71 and when cold?

Thanks,

Tsvetomir

[UrS4boy]

Testing the F60 Idle Switch/G69 Throttle Position Potentiometer

Schematically, this is how the switch wiring shows up:



Based on this schematic, it makes the test procedure a bit easier to understand:

Testing the F60 Closed Throttle (Idle) Switch is as follows:

Across Pins 4 and 6 on the switch:
Closed = 0 ohms (continuity)
Open throttle (slightly) = infinite ohms (open)
If either fails, adjust switch as per procedure above.

Testing the G69 Throttle Position Potentiometer:

Across Pins 1 and 2 on the switch:
Must be 1500 to 2600 ohms

Across Pins 2 and 3 on the switch:
Throttle closed = 750 to 1300 ohms
As throttle is opened from closed to WOT = increase to 3600 ohms
If NO, replace sensor.

More F60 Idle Switch/G69 Throttle Position Potentiometer info here:

http://forums.quattroworld.com/s4s6/msgs/20405.phtml

[UrS4boy]

N71 Idle Speed Stabilization Valve (ISV or ISS Valve) Info

And if the idle switch/throttle potentiometer passes their tests, then move on to the N71 ISV:

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

[doncecone]

10x, Dave! Priceless. What is the connection with the coolant temp. I see the problem only when the car coolant is below 35 C.

[UrS4boy]

G62 Coolant Temperature Sensor info

10x, Dave! Priceless. What is the connection with the coolant temp. I see the problem only when the car coolant is below 35 C.

The G62 coolant temperature sender on the back of the head is the device that tells the ECU that the engine is still cold and needs a) fuel enrichment and b) *maybe* help with the idle stabilization (that is pure wild *** guess - prj will correct me, as needed ). Once the coolant temp goes above a certain temp (maybe 35 C?), then the ECU decides that the engine is warm and no longer needs fuel enrichment.

If the G62 coolant temperature sender is broken, the ECU may "think" its cold out all the time, leading to higher duty cycles on the injectors and, therefore, rich runnng conditions (which, by the way, can burn out the catalytic convertors) and poor fuel economy. Part No. is 035919369M (KATE calls it a thermal switch - No. 9 Illustration 919-65 (A10Q, 1993))(Scroll down and look for Item 9 in the diagram) (Note: the 035919369M G62 coolant sender is a Bosch 0280130037).

From Bentley, the G62 (Engine Coolant Temperature (ECT)) sensor test procedure is as follows:

Allow the engine to cool to room temp (68F/20C)
Disconnect ECT sensor from harness connector
Switch multimeter to resistance range
Connect multimeter to terminals 1 and 2 of the ECT
Resistance must be 1500 to 3000 ohms

IF NO = replace ECT
IF YES = check wiring between sensor and ECM (ECU)

Reference: Bentley pg. J28-22

MORE G62 Coolant Temperature Sensor info here:

http://forums.quattroworld.com/s4s6/msgs/20985.phtml