VR6 running rich! VAG-COM Error and Sensor results within

[Fanjita 1]

Hi all,

 

Sitting in my driveway holding at ~2000RPM to check that the tappet noise wasn't any worse, we all noticed how rich smelling the car was. This was a fully warmed up run, so I hooked it up to my laptop to see if anything comes up.

 

One error is logged and cannot be cleared:

 

00561 - Mixture Adaptation

 

15-00 - Adaptation Limit (Add) Not Reached

 

From what I've read this error refers to the mixture being out of limits at low/idle (additive) stage? I also read that a common cause of this fault is a vacuum leak?

 

I also took time to monitor the sensor readouts, then noticed that these can be logged and recorded. So I have done, results to follow, these were taken whilst stationary on my driveway between idle and 2000 rpm. Hopefully some people in the know can tell me if all the readouts are within limits?

 

Log attached

 

Thanks in advance

James

vagcomlog.pdf

[Fanjita 1]

OK I'm getting suggestions that it might be the Lambda probe, we unplugged it and the car seemed to hold at 2000 revs with a much lower smell of fuel out the back!

 

It's not throwing any fault codes up on the lambda though, what do people think?

 

Please Help!

[Critical_Mass 10]

O2 sensor will show on Vagcom.

[Kevin Bacon 5]

The lambda isn't adjusting much given the vast amounts of unburned fuel you could smell!

 

I would say replace it. Sounds to me like the ECU is happy enough with the signal of the Lambda and it's not duff enough to log a fault code, but is duff, if you know what I mean.

 

Or it could be the old favourite Mr MAF sensor....

[Fanjita 1]

Did consider the MAF, but haven't done anything about that, what's the best way of checking them? I have access to a multimeter but the thing that confused me was how to supply power for the hot wire whilst still taking readings from it.

 

Unless its just a resistance check that I need to do?

[Kevin Bacon 5]

Checking the MAF is complicated as it's not a linear sensor. In other words, full throttle may not necessarioly give the same voltage as the same position on the road. It's all based on air mass / density.

 

In theory, if you unplug the MAF with the engine running and nothing happens, the ECU has already decided the MAF is shot and is using an alternative sensor for load (throttle position). And if the engine dies when you unplug it, you can assume the ECU was using it.

 

Unfortunately this test seems to give different results on different engines because the ECU is only really concerned about the physical connection (OBD1) and not the readings....unless duff....in which case it bypasses it without telling you.

 

As a basic test, you could put a voltmeter across ground and the MAF's output wire (usually red, or red with a blue tracer) and at idle you should see ~ 1.2V and when you blip the throttle the voltage should increase.

[buttles 0]

http://s2central.net/ds_G70.html. Have a read of this. Gives a basic test of the maf