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VR6 low mileage 12-14 mpg and car spec states 29 mpg. After the engine has been running for about 10 mins the car has slow acceleration at low revs in each gear and then it works better at higher revs. I have been told by another VR6 oc member that it could be O2 sensor, vacuum leaks, spark plugs or wires? It feels and sounds like the petrol mix is too rich at low revs so how can I tell if it's O2 sensor causing the low mpg because there were no error messages when the laptop was plugged in at the garage looking for all faults?

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The lambda sensor has a connector mounted on the rear engine mount.

Unplug the lambda connector.

 

Using a multimeter, check the following:

1. Heater Element

- Check you have 12v across the heater element (the two white wires - on the car side of the connector!)

- Check the resistance of the heater element; looking for a few Ohms across it (same two wires as last step - on the sensor side of the connector)

2. Sensor

- check low resistance of grey wire from lambda connector to ECU - pin 42

- check low resistance of black wire from lambda connector to ECU - pin 20

Re-connect the Lambda sensor.

 

If you have VCDS, there may be some measuring blocks to hint at what the O2 sensor is doing:

https://www.ross-tech.com/vag-com/m_blocks/index.html

 

At this point, you may need a new Lambda sensor...

 

I would check for air leaks on the inlet route before buying sensors, though.

 

Have fun!

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