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I am now the owner of a 2007 Audi S6 V10. The vehicle is quite clean despite its 270,000 kms (it is not the original engine, but I do not know its mileage. So let's take it for granted that it has at least 200k )
My problem currently being rough idle. All the coils and sparks have been replaced.
1. I currently have Ignition Open Circuit error codes for cylinders 5,4,3 and 10,9,7 which are causing some missfires. For this problem I have the impression that it is only the connectors which no longer clip on the coils.
2. I have two codes Intake Manifold Flap stuck close. I'll have to do a flap delete or find a new intake. It's not supposed to affect driving from what I've seen on the forums, but I don't know what impact it has on idle.
3. The vehicle is Catless and therefore has no O2 sensor on the catalyst.
4. MAF sensor seems dead. The motor struggles to keep alive if it is plugged in while unplugging the motor varies between 500 and 800rpm.
The engine picks up the RPMs very well. Any hesitation disappears after 1500rpm. I haven't tried it on the road yet, to see if the acceleration is correct or not.
So my question today is:
- Can flap stuck close cause rought idle?
- Could the absence of O2 Cat cause rough idle?
- What are the typical symptoms of valve clogging by carbon?
I will replace the MAFs soon to eliminate this probable cause. I don't know this engine particularly well, but I know that on VR6s for example when the MAF was defective, you unplugged it and it ran correctly.
Copy and paste would be better than pictures. It eliminates typos if more code research is needed.
Regarding flaps stuck closed, it is likely referring to the flap set at the outlets of each side of the intake. These are separate from the long / short runner flaps in the upper center of the intake. Suggest to not be too quick to do a “flap delete” as there are ramifications and a delete is the least desirable.
Regarding deleted O2’s, are the front O2’s still in place or are all the O2’s removed?
If you don’t know when the last intake valve decarb service was performed then you should assume it needs a decarb service.
005491 - Left Engine Mount Solenoid Valve (N144)
P1573 - 004 - Open Circuit - Intermittent
Freeze Frame:
Fault Status: 00100100
Fault Priority: 0
Fault Frequency: 4
Reset counter: 255
Mileage: 270258 km
Time Indication: 0
Date: 2006.05.12
Time: 09:18:45
Freeze Frame:
RPM: 698 /min
Load: 21.6 %
Speed: 0.0 km/h
Temperature: 51.0°C
Temperature: -40.0°C
Absolute Pres.: 1010.0 mbar
Voltage: 13.716 V
- The MAFs are absent so the codes here are normal.
- After checking, no missfire detected with the engine at 1500RPM
- There is no gasket between the Y-Pipe Throttle body and the lower intake, causing a huge vaccum leak. Probably more air enters through there than through the throttle bodies at idle.
- The only two O2 sensors still present are those of the lower cat (see photo; In green I can see, in Yellow im not sure. Very hard to see between the firewall, frame and engine)
- The actuator or central flap mechanism is completely seized. I will see if they are damaged or not by dismantling them.
Fix G42 IAT sensor and see if that stabilizes the MAF’s.
Bank1 and Bank2 flaps stuck closed is controlled by the lowest mounted actuator on the front face of the intake. Maybe check to see if VAG output tests will actuate it. It is possible the long / short runner flaps are disintegrating and plastic bits are wedging the side flaps causing “stuck closed” codes. Both banks are connected to the same actuator so one piece of larger debris in one side flap port could result in DTC’s for both banks.
Check the wiring first but it looks like you need some front O2 sensors replaced. Access is going to be a challenge. Common approach with BXA is replace O2’s when engine is out due to limited access.
Resolve the coil packs open circuit DTC’s as this will cause misfires. This is a V10 so you can have misfiring cylinders above 1500RPM and it may not be obvious like a rough idle because the engine has a lot of cylinders!
Recommend to pull the intake and inspect for broken long / short runner flap system, stuck side flaps both banks, plastic flap debris floating in cylinder head intake ports, amount of intake port carbon accumulation, etc. The intake is considered a wear item as the flap system will eventually disintegrate and if the wrong size bits get into the wrong places then it could destroy the engine. Only way to know the current state is pull the intake and inspect. While intake is off then consider a fuel injector cleaning or replacement service as this can also be a source of misfires, replace all seals and o-rings under the intake especially the oil filter housing, the $25 coolant temp sensor at the lower back of the intake that is very difficult to access with the intake in place, etc.
Fix G42 IAT sensor and see if that stabilizes the MAF’s.
Do you have the schemas for the IAT? I've seen this code, but I have no idea what it is. Can this probe really have an impact on idle? I'm going to have to put a gasket back on (see photo) when I reassemble the intake after the carbon. Because currently it is sucking in air thoroughly from there.
Check the wiring first but it looks like you need some front O2 sensors replaced. Access is going to be a challenge. Common approach with BXA is replace O2’s when engine is out due to limited access.
After checking, I don't have the original headers, but a custom 5-1. O2 sensor level this will be corrected with a custom tune. I won't take the engine out if I can avoid it. Especially if I can tune the engine AND correct this problem at the same time.
Resolve the coil packs open circuit DTC’s as this will cause misfires. This is a V10 so you can have misfiring cylinders above 1500RPM and it may not be obvious like a rough idle because the engine has a lot of cylinders!
All missfire codes disappear with a higher RPM. My tech checked with Vagcom and livedata. No missfire detected Engine I and Engine II during acceleration. I still ordered the kit to redo the coil pack connectors. Some don't click.
Recommend to pull the intake and inspect for broken long / short runner flap system, stuck side flaps both banks, plastic flap debris floating in cylinder head intake ports, amount of intake port carbon accumulation, etc. The intake is considered a wear item as the flap system will eventually disintegrate and if the wrong size bits get into the wrong places then it could destroy the engine. Only way to know the current state is pull the intake and inspect. While intake is off then consider a fuel injector cleaning or replacement service as this can also be a source of misfires, replace all seals and o-rings under the intake especially the oil filter housing, the $25 coolant temp sensor at the lower back of the intake that is very difficult to access with the intake in place, etc.
Thank you for this recommendation. I will make sure to order everything at once.
BXA has two MAF’s with one inside each of the two air filter housings and the IAT sensor is incorporated inside the MAF sensor. Resolving MAF and IAT DTC’s would be helpful for several reasons including one of several steps to resolve misfires. Disconnecting the MAF to check for failure / change in idle observation is a good temporary test and is intended to help determine if MAF sensor needs cleaning or replacement. Careful with MAF cleaning procedure as the filament is delicate.
Front O2’s provide fuel burn feedback to the ECU. The stock BXA has four exhaust banks with four front O2’s. I would be hesitant to have a tune code out the front O2’s otherwise a critical feedback feature of the fuel injection system would be disabled. This is something not normally done with readily available tunes. Some folks tune out rear O2’s to avoid a CEL when running catless exhaust but among other things the exhaust gasses horribly stink without cats especially a V10.
I recall in the past Vag-com usually disables misfire detection as RPM’s rise much over idle. IIRC misfire detection changes to Disabled when revving and returns to Enabled status when idling again. I could be wrong so have a closer if you want to be sure. Either way the ideal goal is to have zero misfires under all operating conditions.
Not trying to make your list longer but since the vehicle is high mileage then recommend to inspect the condition of the alternator belt / tensioner / roller / crank pulley as well.
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Rough idle on V10 2007
