A6 Engine problems, please help

[Javier Neog]

Hi there. This is my first post after looking for the problem for weeks with no results. I really need help.

I have a 2008 A6 Audi 2.8 FSI. Check Engine (MIL) turns on every few days, and I think it happens when day is too hot (near 40° Celcius). While reading to VCD codes I get the following Fault Codes:

I can clear the codes but the first one (powertrain) always appear again immediatly after. After few days Check Engine (MIL) appears again with those "System too Rich" fault codes. Any ideas?

Thank you in advance =)

005748 - Powertrain Data Bus
P1674 - 000 - Implausible Message from Instrument Cluster
Freeze Frame
Fault Status: 01101000
Fault Priority: 4
Fault Frequency: 92
Reset counter: 40
Mileage: 83277 km
Time Indication: 0
Date: 2014.06.04
Time: 20:17:17


Freeze Frame
RPM: 832 /min
Mass Air / Rev.: 169.0 mg/str
Temperature: 31.5°C
Idle
Voltage: 13.26 V
Speed: 0.0 km/h


004407 - Fuel Trim: Bank 1 (Add)
P1137 - 000 - System too Rich - Intermittent - MIL ON
Freeze Frame
Fault Status: 10100010
Fault Priority: 6
Fault Frequency: 6
Reset counter: 40
Mileage: 83458 km
Time Indication: 0
Date: 2014.06.07
Time: 11:37:30


Freeze Frame
RPM: 736 /min
Mass Air / Rev.: 136.3 mg/str
Temperature: 99.0°C
Idle
Time: 1715.2 s
Bin. Bits: 00000010


004409 - Fuel Trim: Bank 2 (Add)
P1139 - 000 - System too Rich - Intermittent
Freeze Frame
Fault Status: 00000010
Fault Priority: 6
Fault Frequency: 4
Reset counter: 38
Mileage: 83458 km
Time Indication: 0
Date: 2014.06.07
Time: 11:37:53


Freeze Frame
RPM: 736 /min
Mass Air / Rev.: 136.3 mg/str
Temperature: 99.0°C
Idle
Time: 1740.8 s
Bin. Bits: 00000010

[Guest 2]

17545/P1137/004407 - Ross-Tech Wiki

17547/P1139/004409 - Ross-Tech Wiki

[Javier Neog]

Thank you Chris.

What do you suggest me to do before sensor replacement? I mean, I can try checking MAF values or Oxigen Sensor values I think, but not sure how to do. First, MAF is not present in my car, it has a MAP so I can't see mg/sec values but mbar values. If you have some additional information I would be so glad with you. This malfunctions seem to be so random and appear every few days.

Thanks!

[MarkTM]

Just a thought but if your car has an EGR valve have you tried to change it or clean it if possible? I know that this can affect cars fitted with MAPS.

[Javier Neog]

Thank you very much Mark! I will try this when the engine gets cooler, as I wasn't able to find it (the valve).

I did the following excercise:

I turned on the engine and let it run idle for some minutes, no acceleration, 700~800 rpm. Lambda control values started from -10% both banks and started dropping within time to -35% bank 1 and -30% bank 2. Is this normal?

[dan2485]

This explains the fuel trims



Your car is a petrol so may not have an EGR valve.

Check your vacuum pipes for leaks and check the air intake is not loose as could be sucking in air and the O2 sensor' s will compensate by adding more fuel.

Dan

[MarkTM]

Dan, you are right was getting EGR confused with a PCV valve, which are fitted to petrol engines almost exclusively. All of the petrol engines I've known have had Positive Crankcase Ventilation. Just got my TLA's mixed up