ABY running rich all the time

[little_e]

My ABY-engine is always running rich.
Fuel consumption is up and turbo boost is down. Via VagCom I get fault codes 00525 and 00537 (O2 sensor short to ground and adaptation limit exceeded).
Lambdavalue in Vagcom at idle is 1,25, suggesting i lean mixture.

This is what has been tried so far:
Replaced O2-sensor.
Measured ECU coolant temp sensor and intake air sensor, they measure okay.
Tested signal wire from O2-sensor to ECU. Checks out okay.
Tested heating to O2-sensor. Tested okay.
Cleaned earth points at intake.
Switched injectors for another used set.
Multifunction sensor was new from Meyle a few months back.
MAF was new from Bosch 18 months ago, I have not tested it.

If voltage at O2-sensor is tested at idle, voltage is about 0,960 volts - suggesting a rich mixture, quite the opposite of the value I read from the ECU in VagCom, but a more trusting value since being behind the car smells unburnt petrol.
Another strange issue is that the lambda value in VagCom is the same with the O2-sensor connected as it is disconnected.

Has anyone got a clue as to why my engine is running rich and turning codes?

[Error404]

Sounds like your ECU is not seeing the lambda sensor. Regardless, that should not cause excessive rich conditions all the time.
If you have done a thorough intake leak test you should test the delivered fuel pressure.
(TIP - unless you already have the fittings & gauge, its cheaper just to replace it

[mike74]

Could a leaky manifold/exhaust pre-lambda cause the same issue?

[little_e]

I have actually replaced the fuel pressure regulator with a new Bosch unit, but it didn't make a difference.
Earlier this year I replaced the exhaust manifold with some eBay RS2 China copy.
Could that really be the culprit?

[UrS4boy]

S2 3B and ABY and RS2 ADU Boost Leak Testing

Has anyone got a clue as to why my engine is running rich and turning codes?

You need to test the intake tract for a boost leak, to make sure that you don't have a problem that is easily solved.

Read this:

S2 3B and ABY and RS2 ADU Boost Leak Testing:

http://www.s2forum.com/forum/showthread.php?t=63974&highlight=boost+leak+testing

[little_e]

I will test for leaks, but can someone tell me how the engine can run rich on idle (and the ECU reporting a lean mixture in Vagcom) if there is a leak?
I'm asking because I just don't know

[domas]

As told before, check ground reference @ sensor and its heater if it is exactly 0V, same with +12v pin at heater.

[little_e]

Oh yeah. I will on Saturday, Domas

[UrS4boy]

G62 Coolant Temp sensor info and reasons why it is important

I will test for leaks, but can someone tell me how the engine can run rich on idle (and the ECU reporting a lean mixture in Vagcom) if there is a leak?
I'm asking because I just don't know

Running rich always results in the need for a boost leak test as a first step in the diagnosis. It cost nothing parts-wise and can reveal several hose leak issues that you weren't aware of.

If you don't want to try that, try checking out your G62 Coolant Temp sensor that the ECU uses to determine whether the engine is up to temp and it can start trimming the fuel back.

G62 Coolant Temp sensor info and reasons why it is important

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

[domas]

those are good to check, but vag com seeing the opposite of lambda falls into totally different category, as far as ecu failure etc.

[mac2226]

My ABY-engine is always running rich.
Fuel consumption is up and turbo boost is down. Via VagCom I get fault codes 00525 and 00537 (O2 sensor short to ground and adaptation limit exceeded).
Lambdavalue in Vagcom at idle is 1,25, suggesting i lean mixture.

This is what has been tried so far:
Replaced O2-sensor.
Measured ECU coolant temp sensor and intake air sensor, they measure okay.
Tested signal wire from O2-sensor to ECU. Checks out okay.
Tested heating to O2-sensor. Tested okay.
Cleaned earth points at intake.
Switched injectors for another used set.
Multifunction sensor was new from Meyle a few months back.
MAF was new from Bosch 18 months ago, I have not tested it.

If voltage at O2-sensor is tested at idle, voltage is about 0,960 volts - suggesting a rich mixture, quite the opposite of the value I read from the ECU in VagCom, but a more trusting value since being behind the car smells unburnt petrol.
Another strange issue is that the lambda value in VagCom is the same with the O2-sensor connected as it is disconnected.

Has anyone got a clue as to why my engine is running rich and turning codes?

Hi little e I have same problem at the moment does your car idle funny when you first start it? sometimes my car takes a few turns to start the car but it eventually starts once up to temp it drives fine but it still smells of unburnt fuel a lot and it says I'm doing 9mpg I've ordered the g62 sensor as this could cause these symptoms.

[little_e]

My problem was that the double shielding in the wire from ECU to the O2-sensor had gone bad, causing a grounding problem in that wire. I replaced the wire with a new, OEM wire, making the car run like a dream again.

[domas]

so grounding problem it was glad you solved it