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Audi D3 W12 2004 camshaft sensor - engine runs rough
Hi everyone!
I often read topics here but never post anything. However I have now a W12 D3 and I would like to share some thought with you before I start working on her.
My Audi W12 from 2004 engine code BHT runs a bit rough especially when cold and on idle.
I plugged the car on VCDS and found the following code on engine II;
-G301 Exhaust camshaft position sender/cylinder bank 2
-G28 Engine speed sender
So there seems to be some incorrelation between the G28 and the G301. One would think the problem is then in the G301 else, if the problem was with the G28, the other cam position sensors would be incorrelated as well.
As far as I could find out using SSP the G301 is the Camshaft position sensor mounted on the drivers side bank 2, so it is the most outwards placed sensor of the left bank correct? (see photo below in yellow).
The cam adjustment range is about 1.0'KW or max 5%. BTDC ATDC values are small.
I contacted the dealer but they told me there are no separate cam shaft sensors are being sold, only a complete unit 07C109204J.
Reading some other topics I found that the G301 should be Audi partnumber 06A905161A or Bosch number 0232103019, which I ordered.
Some websites also give the Audi part 030907601 as the correct part number for camshaft sensor, so I ordered that one too.
The G28 crankshaft sensor has Audi part no. 070907601A. Will only replace that after G301. Before I start working on this W12 and replace the G301, do you guys think this is the correct step to be taken?
I've read some topics where people tell the problem comes from bad knock sensors or problems with the choke program for a cold engine. I noticed with VCDS the following things;
-I have measured the voltage of the knock sensors and they are all 0.5-0.7V except the ones from Cylinder 9 and 11, which are- 1.0 and 1.4V.
-The Lambda sensor heating of bank 3 (heater condition Bank 3 Sensor 1) and bank 4 (heater condition Bank 4 Sensor 1) are continiously and rapidly switching between ON and OFF every 0.5s or so.
-The misfire counter is disabled. 0 misfires are detected. Is there maybe something wrong here?
I also ordered some new oil and filter for her. Ravenoil 0W30 VSW.
There seems to be difference in the W12 engines produced before or after 2005. Dry sump vs wet sump engine.
My model with BHT (or BSB BTE) engine should hold 12.5 liters.
Yes, bank two exhaust sensor will be the outer sensor on the USA/Continental Europe driver's side.
See my prior posts on the "how to." Same approach as for the coolant temp sensor, which is virtually right next to that cam sensor. Basically you pull the upper intake manifold assembly to get (just barely) enough access back there. Motor does not come out with that technique and work scope goes from dozens of hours and $$$$ to a half day and $$$.
If you are doing the cam sensor there and the coolant sensor has not been replaced, I would do both at same time. In all cases it is "when not if" for these sensors. The exhaust heat appears to affect them and also causes the wiring insulation long term to deteriorate. Plan to repair wiring damage at same time, and to replace the end connector on the wire that plugs into the sensor. Audi sells those as piece parts.
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In my case, I eventually lost the other side too (USA/Continental Europe) passenger side. Same issue with the heat, and on that side the wires got more toasted. The intake sensors are father away from the exhaust manifold area so don't seem to come up as an issue.
The D3 W12 is conventional wet sump. Audi's W12 documentation for the W12 is flat out wrong in its reference to dry sump. They seemed to cut and paste from a prior engine version in what they published. Capacity of USA BSB is 13 quarts. Original fill was a 0W30 503 compliant. 503 has been replaced by 504. In USA they only used 502 compliant, which was typically 5W40. Mobil 1 0W40 was listed in the days of 503 spec as 503 compliant (in addition to 502)---among the very few that were. With 504 now, that would be the optimal if you want to stick to spec. The 504 oils are often branded as "ESP" and are more common in Europe than here in USA. You have to have low sulphur gas, which was the older hang up with 504 oils in USA. But at least in California we have the very low sulphur gas, and Audi is now shipping vehicles in with 504 original fill.
I don't really follow what your issue may be with O2 sensors. It sounds like maybe you are discussing a theoretical issue rather than one found on your car code wise? (besides the rough running that is; more in coming paragraphs) If no codes tie to sensors, I would leave it alone. The most common issue with W12 O2's turns out to be the connectors, not the sensors. There is a TSB on it. You replace the connector on the car harness side and splice in 6-12 inches of new end terminal conductors that plug into the connectors. Audi sells the piece parts for it. BTDT on a couple of mine, and wiring rather than sensor change (tried both) is what resolved it. Search for my prior posts.
Net, I would replace the coding cam sensor on USA driver's side, and do coolant sensor preemptively if not done before. Up to you on whether do do passenger side too, or wait til later. I did each one as it came up, so manifold was off three times. I did spark plugs at same time in one case, since the same upper manifold pull is the easiest and most cost effective way to do them. I would not do crank sensor (if even needed) until after changing cam sensor, since cam sensor is the known and likely issue.
Last, if you clear codes you should find check engine light goes out and running is better, briefly. Within two engine cycles and some driving check engine light will return. At the moment it does, you may feel motor get a bit rougher. The car is going into a fail safe mode to protect engine in case cam drive system is actually screwed up--which affects the cam/valve timing. That is probably where your rough running feel is coming from, as opposed to some O2 sensor issue. The safe mode aspect is covered in the W12 technical materials. Again, replace cam sensor, clear codes and then hopefully resolves in full.
Report back with findings to close the loop on thread and issues. It helps us to have completed reports on what was actually found and done.
Yes, bank two exhaust sensor will be the outer sensor on the USA/Continental Europe driver's side. Thanks.
See my prior posts on the "how to." Same approach as for the coolant temp sensor, which is virtually right next to that cam sensor. Basically you pull the upper intake manifold assembly to get (just barely) enough access back there. Motor does not come out with that technique and work scope goes from dozens of hours and $$$$ to a half day and $$$.. Will try to do this job in about 2 weeks and update the forum with some pics.
If you are doing the cam sensor there and the coolant sensor has not been replaced, I would do both at same time. In all cases it is "when not if" for these sensors. The exhaust heat appears to affect them and also causes the wiring insulation long term to deteriorate. Plan to repair wiring damage at same time, and to replace the end connector on the wire that plugs into the sensor. Audi sells those as piece parts. Good advice.
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There is a TSB on it. You replace the connector on the car harness side and splice in 6-12 inches of new end terminal conductors that plug into the connectors. Audi sells the piece parts for it. BTDT on a couple of mine, and wiring rather than sensor change (tried both) is what resolved it. Search for my prior posts. Good thing to keep in mind, will order some extra connector and wiring at Audi. You can indeed order them separate together with some new wiring (male/female that just plugs in)
Net, I would replace the coding cam sensor on USA driver's side, and do coolant sensor preemptively if not done before. Up to you on whether do do passenger side too, or wait til later. I did each one as it came up, so manifold was off three times. I did spark plugs at same time in one case, since the same upper manifold pull is the easiest and most cost effective way to do them. I would not do crank sensor (if even needed) until after changing cam sensor, since cam sensor is the known and likely issue.
Last, if you clear codes you should find check engine light goes out and running is better, briefly. Within two engine cycles and some driving check engine light will return. At the moment it does, you may feel motor get a bit rougher. The car is going into a fail safe mode to protect engine in case cam drive system is actually screwed up--which affects the cam/valve timing. That is probably where your rough running feel is coming from, as opposed to some O2 sensor issue. The safe mode aspect is covered in the W12 technical materials. Again, replace cam sensor, clear codes and then hopefully resolves in full.. Engine light is now off also.. which I think is a bit strange.
Report back with findings to close the loop on thread and issues. It helps us to have completed reports on what was actually found and done. Will do keep guys updated about the W12. Really good to find so much detailed and specialist information here.
So today i started working on the W12. About 5 hours spent.
Aim is to change G301 sensor, temperature sensor, change oil and filter, spark plugs.
Engine seems to have a vacuum leak. The oil vent system seems to be dirty, the coolant water is dirty and 1 hose is leaking at a T-joint.
Lets check;
Start working on the W12
Air intake manifold off. Lots of hoses to be disconnected.
Actually two parts on the bottom side are damaged and leaking oil where the oil vent line joins the intake manifold. Will clean and fix that tomorrow.
W12
Intake manifold off
The Tpiece that leaked brownish water. One line runs from the top of the coolant water resevoir to this Tpiece.
This was the T-piece
This T-piece is broken. The unit is only sold complete at the dealer for EUR170. Will try to find another solution.
Loosen clamp that holds cables to the back end to create space
Rubber pushed inside to create more space
Disconnected wires put aside with tie-rap to create space
Airco lines pushed aside to create space
Did I mention some space is needed...?
The G301 sensor
Wires of G301 plug.Will clamp on a new one tomorrow. 5Euro at the dealer.
There is the bolt. 5mm Hex.
Maybe reachable trough here?
I tried to reach the bolt of the G301 trough the left front wheel arch space.
In the end, I just took a 5mm allen key and sticked my hand in between the narrow space behind the engine. Enough space to turn. Bolt and sensor came out in 5minutes.
I changed the temperature sensor too. It has a small clip that holds the sensor. Pulling out was easy. Getting the clip in, not.
Will try tomorrow with a small mirror... because i dropped the clip somewhere behind the engine
Now looking for information about removing the air procedure for the coolant water, somewhere on the engine there should be venting valves.
Also the temperature sensor clip needs to be ordered, a Tpiece.
Need to repair the intake manifold as the downside is cracked.
To be complete, I removed a part of the engine bay protection at the rear, that is fixed with 10mm plastic bolts.
Also I loosened the 13mm bolts that hold 1 heat protection cover and pushed the heat protection cover aside to create more space.
Coolant sensor clip: Yes, you will drop it. Way harder to get in than get out because of new o ring. With new clip, tie a long piece of dental floss to it. Then if (when) you drop it again, you can just fish it out. When it's done/in place, just trim off all you can.
You should replace that coolant line back by rear of motor and coolant bottle--#10 in diagram. Pricy but it will crack and break from the heat soak. Over the years the Wye in hose 5 (near front upper radiator hose) also rotted out on mine. Upper large plastic connector at large hose that goes into top of water pump also started pulling out at the factory crimp clamp. Inspection showed the plastic connector was slowly rotting out. Easier to do that hose w/ upper manifold out like you have it now.
BTW, look at motor torque mount up in front of (continental Europe) passenger side of motor. Forward of the main mount on that side; can just barely see looking down on that side along front side of air box. By your years and likely miles, probably blown unless replaced before. Really hard to replace, but at least inspect it.
Guessing you have some broken or cracked oil breather hoses too--starting with that one on the front right on the upper intake in picture. Also pricy; may be able to bandaid at least for a while with some heavy rubberized tape, like used to wrap underground gas pipe for example. BTDT.
One more item: when you pull spark plugs, look for some weird corrosion/pitting inside of the holes in the valve covers where the coil packs pass through. As I learned from one of the other W12'ers here, that is a sign the coil pack is bleeding spark out the side and eating out the valve cover metal. I never had ignition codes, but it was clear mine where leaking current at some point. They were recalled by Audi (along with boatloads of other Audi/VW vehicles), but I don't know if damage was pre or post the recall replacement by dealer. Dealer said nothing about it, but par for course with other damage I found they band aided or didn't tell me about, including that plastic hose #10 they spliced with some rubber hose and clamps.
10-20-2018, 01:29 AM
Audi D3 W12 2004 camshaft sensor - engine runs rough
keep guys updated about the W12. Really good to find so much detailed and specialist information here.
