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- City
- cheshire
- State
- WY
- Country
- United Kingdom
- What I Drive
- 2010 audi s4
Hi I have a 2011 audi s4 avant CAKA engine. I have been having a problem with the car setting a fault codes P0172 and P0175. It takes a few drive cycles for the fault codes to set. I have checked the fuel trims and confirmed they are working hard to correct the fueling total fuel trim around - 30 for both banks with stft and ltft.
The following work has been carried out. The PCV has been changed to a brand new one and sw checked at audi to confirm up to date. The intake ports have been cleaned with supercharger removed and intake flaps cleaned and operation confirmed OK. The intake system has been smoke tested for leaks none found. The N80 charcoal canister purge valve has Been removed and inspected and tested no defect found, also confirmed with removed still running rich. It has been replaced anyway with new original part.
The lambda probes have been tested both before and after cats as OK, but to be certain both have been replaced on Bank 1 to observe if any different, no difference after replacing.
A compression test has been carried out all cylinders within specification. All the spark plugs were similar in appearance all quite black. No obvious wetness or any cylinder looking different to others. Based on this doubting Injector problem. No misfires are detected and fuel trims show worse at idle, and improves under load. All spark plugs have also been replaced.
An interesting observation was that if I cleared fault memorys, in so resetting fuel trims a d started the car the fuel trims would be in an acceptable range. And if I were to drive the car for a long drive over 40 mins or so they would still be acceptable. If I turned the car off and started it again instantly they would still be good. If however I turned car off and let it go to sleep, so locked and turned off for 5 to 10 mins then restart instantly the fuel trims go very negative. Investigating this further I noticed the calculated air mass value to be different in both situations. When running rich around 150mg/st at idle and warm, when not faulting around 100mg/st. So if the ecu computes more air it will add more fuel.
The car uses speed density engine management no air mass meter, so have checked the wiring integrity of all the map sensors all confirmed OK. Also the readings checked against a gauge and are reading correctly. As a matter of course all 3 map sensors have been replaced and still no change. The throttle body has been cleaned and tested OK, the supercharger bypass valve cleaned and inspected no obvious defect. All basic settings carried out but still the same.
I'm running out of ideas as to what could be causing this. I have no donor car to check values against. And would like to confirm whether my air mass readings are wrong and as such this is causing rich running, or does the ecu go through a learning phase when faults cleared and it is normal for air mass readings to lower when you clear fault memory's. Or if anyone has some air mass readings at idle so I can confirm whether mine are wrong or right. Any help or advice is appreciated.
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The following work has been carried out. The PCV has been changed to a brand new one and sw checked at audi to confirm up to date. The intake ports have been cleaned with supercharger removed and intake flaps cleaned and operation confirmed OK. The intake system has been smoke tested for leaks none found. The N80 charcoal canister purge valve has Been removed and inspected and tested no defect found, also confirmed with removed still running rich. It has been replaced anyway with new original part.
The lambda probes have been tested both before and after cats as OK, but to be certain both have been replaced on Bank 1 to observe if any different, no difference after replacing.
A compression test has been carried out all cylinders within specification. All the spark plugs were similar in appearance all quite black. No obvious wetness or any cylinder looking different to others. Based on this doubting Injector problem. No misfires are detected and fuel trims show worse at idle, and improves under load. All spark plugs have also been replaced.
An interesting observation was that if I cleared fault memorys, in so resetting fuel trims a d started the car the fuel trims would be in an acceptable range. And if I were to drive the car for a long drive over 40 mins or so they would still be acceptable. If I turned the car off and started it again instantly they would still be good. If however I turned car off and let it go to sleep, so locked and turned off for 5 to 10 mins then restart instantly the fuel trims go very negative. Investigating this further I noticed the calculated air mass value to be different in both situations. When running rich around 150mg/st at idle and warm, when not faulting around 100mg/st. So if the ecu computes more air it will add more fuel.
The car uses speed density engine management no air mass meter, so have checked the wiring integrity of all the map sensors all confirmed OK. Also the readings checked against a gauge and are reading correctly. As a matter of course all 3 map sensors have been replaced and still no change. The throttle body has been cleaned and tested OK, the supercharger bypass valve cleaned and inspected no obvious defect. All basic settings carried out but still the same.
I'm running out of ideas as to what could be causing this. I have no donor car to check values against. And would like to confirm whether my air mass readings are wrong and as such this is causing rich running, or does the ecu go through a learning phase when faults cleared and it is normal for air mass readings to lower when you clear fault memory's. Or if anyone has some air mass readings at idle so I can confirm whether mine are wrong or right. Any help or advice is appreciated.
Sent from my ELE-L09 using Tapatalk
