Ongoing MAP sensor issue

[mcbuck]

Posting with the hope that someone else has dealt with this or has an as yet unconsidered solution. Will try to keep it brief.

Recently replaced both PCV valves due to failure. Used OEM parts and replaced the whole assemblies.

The next day got multiple faults - ECS fault, rear diff fault, TPMS fault, and a bunch of secondary codes including P0106 - manifold absolute pressure/barometric pressure circuit range/performance. Found a couple of threads that pointed to bad MAP sensor. Replaced it, reset the codes and rocked on for about a week with no further issues. Note - there was oil on the original sensor.

The faults started popping up again on a daily basis, then stopped for about 2 weeks. Now they are back. Pulled the new sensor and it has oil on it also. First thought - sensor is getting oil fouled and causing issues.

So, I have gathered some information (thanks James and Michel) and have a basic understanding of how the oil separator works downstream of the PCV valve, but I can't reason through a failure of that system that would result in excess oil in the intake. I have not pulled the new PCV valves and disassembled them for inspection, but would hope that new OEM parts would not be the issue.

I haven't noticed unusual oil consumption that would indicate excessive blowby gases/worn rings. I also haven't noticed any decrease in performance.

Possible issues -
Faulty wring to MAP sensor (someone else had that issue). Wiring and connector all look good, but I haven't done any electrical testing.
Faulty oil separator resulting in excess oil carried into intake. Requires pulling valve covers to inspect those.
Somehow the result of carbon buildup? Can't reason through that, as cold start misfires seem to be the first symptoms of excess carbon, and I'm not experiencing that.
PCV valves - makes the most logical sense as I changed those immediately before this began.
Battery on it's way out. Have read where this may result in funky codes and faults. Battery is original but shows no other indication of weakening.

I'm currently stumped and don't relish the idea of going to Audi and having them play parts darts.

Any suggestions or troubleshooting tips are appreciated. Until then I'll just keep resetting my faults on a daily basis and assume that she will fix herself eventually.

[wkhanna]

i am no expert, by far.....

..but what i have noticed after sifting prolly thousands of posts is that random faults can be thrown due to a low performing battery.....

...just a though.... ? shot in the dark, as it were.....

[Ape Factory]

I've been looking over the FSM and I actually can't find the MAP sensor or where the actual oil separator is. You mentioned it's under the valve cover but I would think it would be near where the PCV valves are or under the intake manifold?

But I do think you're on the right track. If the MAP sensor is all oiled up after just being cleaned, it has to be a PCV issue. You've never carbon cleaned?

Not our cars but a 4.2L none the less...

[mcbuck]

I've looked at so much that I don't remember where half of it is.

From the self-study program for VAG 4.2l V8 4V FSI - "To minimise the oil contained in the blow-by gases, they are separated via a labyrinth oil separator in the cylinder head cover and a three-stage cyclonic micro oil separator." I have yet to find a diagram of our specific setup, it's a great mystery! The diagram above shows a single integrated PCV valve and separator. We have 2 diaphragm regulating valves that are exposed to intake vacuum between the throttle body and the intake plenum. Since it seems these valves discharge directly into the intake, it would stand to reason that the oil separator would have to be upstream, which leaves inside the valve cover. Feel free to shoot holes in my theory.

If there is an issue there, possibly not draining the separated oil back into the sump, and it is getting carried into the intake.

As for the MAP sensor, it's a combination pressure/temp sensor located on the front of intake manifold just below the top of the radiator.

See diagram from FSM. MAP is #2 and regulating valves are 12 and 16.

IMG_2282.JPG

[Ape Factory]

So if you go back to the FSM, there's a plate below the intake manifold that's attached to the engine block in the engine's V...and it has a crank case breather hose coming off of it. I suspect it's actually in there, under the plate. There's zero room for anything like an air/oil separator under the valve covers but I'll double check.

[mcbuck]

I’ve seen that. Best I can surmise, that pulls air from the passenger side intake tube after the filter to flush fresh air through the valley and across each valve cover to help remove blow by gases.
Got a pm in to Vincenzo in the customer experience forum to see if he can help clarify construction and function.


Buck
Sent from this little electronic gizmo

[Ape Factory]

Here's an expanded view of the head. Nothing in there. The two cylinders are sensors (9, 15, cam position if I remember correctly).

[mcbuck]

Continuing down the path to enlightenment. 99% sure the oil separator is integrated into the valve cover. Small detail but most of the descriptions say "IN the cylinder head cover", not "under". Also found a write up for the oil separator on the VW 3.6 VR6 which shows it built into the valve cover, so it's already been done by VAG.

Note the pics below. The top view of the valve cover - on the bottom right of the pic is where the regulating valve pulls from the crankcase. Notice the raised area that runs the length of the valve cover. Now look at the bottom side of the valve cover - notice the top left of the pic is an opening (on the opposite end) that I betcha a dollar is where the blowby gas is pulled into that tract, hence would lead to the belief that the oil separator is there. The small circular detail in the bottom right of the pic looks like it could be the gravity drain from the oil separator, but that is just conjecture.

IMG_2284.JPG

IMG_2283.JPG

If I am correct, still doesn't answer how to troubleshoot or if there are any user serviceable options other than replace the entire valve cover. Also doesn't help address the MAP issue, but understanding is the first step in problem solving.

Got a 5mm borescope on the way, so will have some fun seeing what I can see with that.

[Hey_T_S5]

You stated it yourself on your initial post...the newly change PVC valves are the most logical reason why you are having these problems. That would be the first place I check as that’s the last thing you changed.
Figuring out how everything else works is great knowledge, specially or you like working on cars but it can lead you into a never ending rabbit hole.


Sent from my iPhone using Audizine

[Ape Factory]

Continuing down the path to enlightenment. 99% sure the oil separator is integrated into the valve cover. Small detail but most of the descriptions say "IN the cylinder head cover", not "under". Also found a write up for the oil separator on the VW 3.6 VR6 which shows it built into the valve cover, so it's already been done by VAG.

Note the pics below. The top view of the valve cover - on the bottom right of the pic is where the regulating valve pulls from the crankcase. Notice the raised area that runs the length of the valve cover. Now look at the bottom side of the valve cover - notice the top left of the pic is an opening (on the opposite end) that I betcha a dollar is where the blowby gas is pulled into that tract, hence would lead to the belief that the oil separator is there. The small circular detail in the bottom right of the pic looks like it could be the gravity drain from the oil separator, but that is just conjecture.

IMG_2284.JPG

IMG_2283.JPG

If I am correct, still doesn't answer how to troubleshoot or if there are any user serviceable options other than replace the entire valve cover. Also doesn't help address the MAP issue, but understanding is the first step in problem solving.

Got a 5mm borescope on the way, so will have some fun seeing what I can see with that.

I'm guessing that's just a baffle honestly. I can't see that thin space holding a complex air/oil separator with a valve. Let's see what the bore scope reveals! I need one of those, LOL.

[Ape Factory]

mcbuck,
You were RIGHT. The air/oil separator is indeed in the valve cover. Found confirmation of this tonight.

"The CFSA engine also had a crankcase ventilation system which captured blow-by gases for combustion. To minimise the oil contained in the blow-by gases, the gases passed through a labyrinth oil separator (in the cylinder head cover) and a three-stage cyclonic micro oil separator."

What I don't know is where that three stage cyclonic micro oil separator is. I can't find reference to it in the FSM anywhere. Unless the labyrinth separator and the cyclonic unit are all in the valve cover.

[midam96]

Have u resolved the throwing of the codes? Fwiw I have found the Internet to b unreliable parts wise on what is sold “OEM” n China is not the same as an Audi supplied part.
I’m really interested in your final resolution certainly hope u have found the gremlin.

[midam96]

Resolution to my Rs throwing codes, tpms,abs,sport differential apparently was Manifold absolute pressure sensor gone bad. Drove back the 75 miles from dealer no codes were thrown on return. I’m going to reserve final judgement on the problem being totally resolved for another week of driving. Not sure if this is every Rs’s issue on code throwing but it was best answer I’d gotten so far.

[RenSport30]

Posting with the hope that someone else has dealt with this or has an as yet unconsidered solution. Will try to keep it brief.

Recently replaced both PCV valves due to failure. Used OEM parts and replaced the whole assemblies.

The next day got multiple faults - ECS fault, rear diff fault, TPMS fault, and a bunch of secondary codes including P0106 - manifold absolute pressure/barometric pressure circuit range/performance. Found a couple of threads that pointed to bad MAP sensor. Replaced it, reset the codes and rocked on for about a week with no further issues. Note - there was oil on the original sensor.

The faults started popping up again on a daily basis, then stopped for about 2 weeks. Now they are back. Pulled the new sensor and it has oil on it also. First thought - sensor is getting oil fouled and causing issues.

So, I have gathered some information (thanks James and Michel) and have a basic understanding of how the oil separator works downstream of the PCV valve, but I can't reason through a failure of that system that would result in excess oil in the intake. I have not pulled the new PCV valves and disassembled them for inspection, but would hope that new OEM parts would not be the issue.

I haven't noticed unusual oil consumption that would indicate excessive blowby gases/worn rings. I also haven't noticed any decrease in performance.

Possible issues -
Faulty wring to MAP sensor (someone else had that issue). Wiring and connector all look good, but I haven't done any electrical testing.
Faulty oil separator resulting in excess oil carried into intake. Requires pulling valve covers to inspect those.
Somehow the result of carbon buildup? Can't reason through that, as cold start misfires seem to be the first symptoms of excess carbon, and I'm not experiencing that.
PCV valves - makes the most logical sense as I changed those immediately before this began.
Battery on it's way out. Have read where this may result in funky codes and faults. Battery is original but shows no other indication of weakening.

I'm currently stumped and don't relish the idea of going to Audi and having them play parts darts.

Any suggestions or troubleshooting tips are appreciated. Until then I'll just keep resetting my faults on a daily basis and assume that she will fix herself eventually.

Did you ever find a solution? Currently experiencing this same problem and would love any information to help track down a solution. Thank you!