Bank 1 & 2 intake manifold flaps stuck OPEN

[Darel]

Hi guys,

'09 S5 4.2 V8 with the VACUUM intake flaps (not the mechanical ones with the problematic linkage).

CEL just popped up today. I have a hard fault, resets but immediately returns. Both banks 1 & 2 intake flaps stuck OPEN. Both faults appeared at the same time.

Full disclaimer: just finished replacing an injector and doing a carbon clean on the car about 3 weeks ago, have about 1500 trouble-free miles on the car since then.

I do recall, correct me if I'm wrong, that the flaps are normally closed and application of vacuum opens them. So my first thought was one of the vac lines I worked on popped off, but that would cause them to register as stuck closed, not open, no?

When I reinstalled the manifolds, I did use my MityVac to open the flaps while torquing down the LIMs as the manual states, and they did work just fine for a few weeks.

Also, while I had them off I cleaned them up with carb cleaner / brake cleaner, it's possible some got into the potentiometers and ruined them I guess, but I think it would be REALLY unlikely they failed simultaneously.

Car's running fine, just have a CEL on, no EPC or misfires, or rough running or anything.

Also noticed I have an intermittent knock sensor 4 low signal fault, 2 occurrences in 2 weeks. Will address in a separate thread but figured I'd mention it in case it's somehow related (highly unlikely).

Any thoughts on where to begin on this one?

[Ape Factory]

The vacuum flaps you mention and the problematic linkage that can go faulty are one in the same. You're right in their natural position is closed and the linkage/solenoid opens them at a predetermined rpm point. Check the linkage and check the solenoids. If a line popped off, I'd assume they'd be "closed" unless, and it's quite probable, that our closed is Audi's open. Germans.

[Darel]

Yeah it's got to be a vac leak or something. Probably not too big a deal, but since I'm occasionally getting that knock sensor fault I'm just going to go ahead and put it in service position and lift the UIM (in the most minimally invasive fashion) to replace the sensors, and look at it then. I remember having a nightmare of a time getting that one vac line at the front on, the one that points straight down. Maybe I didn't get it on all the way.

Any issues with continuing to drive the car with the flaps open? Logic tells me no, but....Germans.

[Darel]

OK so I dug into this a little bit today and I'm more confused. Could not initially get the CEL to reset by clearing the codes, even though the fault was only showing one instance. So then after going through the VCDS and clearing codes out of everything (pending, active, etc) it reset, and did not return. Great, right?

Left the Vag-Com hooked up and monitored the flaps as I went for a drive. No matter what, on both banks, under all driving conditions, the Position (spec.) was 99.6. Anytime the engine was running, 99.6 on both banks. I am operating under the assumption this is the commanded value - in other words the car wants both intakes 99.6% open.

The Position (act.) - which I am assuming is actual - varied between 80-85%, again under all driving conditions, with the #1 bank just a percent or two less than the #2 bank. This difference I'm not worried about, probably just a difference in the calibration of the pots or something.

I drove the car for about half an hour, trying to get the most varied set of conditions - 4th gear uphill starts, idle, WOT, high-vacuum downshifts - no changes to any of the values. The spec remained locked on 99.6. The actual floated around +- 3%, which I would expect. But, the actual never got close to the commanded 99.6% (highest was 85%) and really, why didn't the spec change for any reason? I am quite certain I am reading Act and Spec correctly since when I shut the engine down, the Act remained in the 80s and the Spec dropped to zero - in other words, the computer shut off and was not commanding anything, but with the solenoid closed the system still held vacuum thus the flaps held position. Then, if I turned the ignition on without starting the car, all values dropped to zero - again what i would expect to see, since the computer doesn't care what position the flaps are in, therefore no command, but the solenoid is triggered on startup so it loses that stored vacuum and the flaps drop to zero. This also tells me the flaps are not stuck, and the pots are working, although I don't know if I should be concerned they only go to 82-85%.

The CEL did not return, FWIW.

Am I overthinking this? Should I just be glad the code cleared?

Oh yeah, no vac lines disconnected, no leaks detected, running the self-test through the vag-Com seemed to go fine but it'd be nice if I could figure out how to command the flaps through the Vag-Com, rather than just listening to it trigger the relay for a minute.

Am I missing something here?

[Darel]

OK, disregard most of that. As soon as I got in the car to go to work this morning the CEL popped back up. The one driving condition I did NOT try with the VAG-COM running was cold start.

So is that really ALL this overcomplicated system does is basically act as a choke? I definitely had some hesitation pulling out of the driveway, gone by the time I got any heat into the engine, basically by the first stop sign a quarter mile away.

[Darel]

Anyone know if there's a way I can manually cycle the flaps in VCDS?

[Darel]

So without puling the UIM I smoked the vacuum system and found a hose out front that had worn through, causing a pretty good leak. Great, right? Nope. No change, still get the CEL with simultaneous banks 1 & 2 flaps stuck open faults. Fixed the vac leak and I don't have any more smoke showing up anywhere so I have to assume now that the issue is under the manifold, and NOT a vacuum leak. Guess I have to pull the manifold. I have a few questions, hopefully you can help me out because this will be the second time this month I pulled the manifold, and I do NOT want to do it a third time.

1. Is there any way to manually cycle the flaps using VCDS? Not the "system tests" that just pulses them for a couple inutes, like where I enter "80%" and can watch to see if they move to the setpoint.

2. Are they normally open or normally closed? I just dont remember from when I had this apart last month. In VCDS when I am watching real time data and it says "Flap position (act) 84%", does that mean it is 84% open or 84% closed? I.e. mostly open or mostly closed?

3. I am getting BOTH banks faulting SIMULTANEOUSLY so I know it is not a problem with the linkage binding or the actuator, or one of the pots reading wrong, but somewhere in the control or vacuum system. If the solenoid under the manifold is not working correctly, would the flaps get stuck open or stuck closed?

4. How can I test that solenoid? What ohms should I be seeing across the terminals?

5. What can you tell me about the "intake manifold change-over valve vacuum actuator" front and center on the manifold? What does it do? How can I check to see if that's the problem?

Trying to arm myself with a number of things to check, and looking for a definitive solution to this once I pull this UIM again. I do not want to do it a third time. Thanks for any info you can give me.

[Darel]

What exactly does the change-over valve do, if you already have separate actuators for each bank? Why the third actuator?

[Darel]

File this one under promising, but annoying:

Went out with the hand vacuum pump, VCDS and multimeter to do some testing today.

Checked resistance on the changeover solenoid, 30 ohms, that's fine.

Vac-pumped all the actuators, they are all fine.

Smoked the system from the blue vac reservoir in the inner fender, all good.

Put the vac pump on the tee, in place of the changeover actuator and pumped up the system. Both bank flap actuators pulled in. I thought this was odd so I checked the new solenoid, and yup, it's normally closed. I shouldn't have vacuum passing through from the tee to the bank actuators.

Ran output test sequence in VCDS. Could hear all of the solenoids actuating. Let the bank actuator run for its' full minute.

Start car. For the first time ever, the CEL went out on its own (without being reset) and both bank actuators read 99.6% exactly on both spec and actual. This I have NOT seen before, previously the best I ever saw was 80-84% act and spec 99.6%. I never saw them agree.

Thinking that the solenoid is sticking, and decided to start working today, I put a couple drops of oil down the vac lines from each bank actuator. This will pass through the solenoid and if it's fouled, loosen it up further.

My line of thinking is that maybe the mineral oil vapors from smoking the living hell out of the entire system did some good for the solenoid.

Again, I am willing to pull the UIM to change the solenoid but I want to make DAMN sure that's the problem before I go through that hell. I am getting closer to confirming the solenoid is sticking. I am going to run the car through several cold starts over the next few days and see if the CEL comes back. I have a week or two since I have the front bumper cover out being painted anyway.

I am also closer to answering some of my own questions, which is actuator pulled in = flaps closed (this is how my car sits at idle) and when the VCDS reads "99.6%" that means it is 99.6% closed. This also tells me the flaps fail open, which makes sense because at WOT vacuum is low and less would be available to pull them in, and at idle vac is high, and pulling the flaps closed would be no problem.

Still curious what that changeover doohickey does. Although I did verify it's working fine.

[Darel]

No dice. Cold start this morning and the CEL returned. However, it may be important to note that the CEL does not pop up immediately, but when the idle drops to normal after a couple of minutes.

[Darel]

Soooooooo I replaced the solenoid, and ran a test on it in VCDS and it went fine. Smoked the vac lines again just to be safe. Put everything back together. Checked everything in VCDS again just to be sure. Started the car up, no codes, no issues. Great. Let it warm, no issues, stopped/started it a few times and got a CEL. DAMMIT. The damn brand new solenoid waited until I had everything put back together and even had the audacity to give me a false sense of hope before the damn thing crapped out. Worked for maybe 20 minutes. Now, no clicky, no nothing when I run a test on it. So when (another) new one gets here that'll be the third time pulling the god damn manifold.

[Darel]

FYI I did confirm once I had the old solenoid out that it had failed mechanically. It was showing 30 ohms so right on there, but was constantly open.

[jg900rr]

Hi. I have a 2015 RS5 with the 4.2 engine in it and I have the exact same problem as you. What was the final resolution? Replacing the throttle valve modules or the Intake manifold flap potentiometer? As I don't see any solenoids in the parts for the intake. Once the car is warm, the EPC/CEL lights come on and the error it throws are both Intake Manifold Flaps are stuck open. The car idles high at start and mostly goes back to normal when driving, but every time I reset the error it comes back. I have vacuum tested it and smoke tested it with no issues.

[Ape Factory]

Hey! You're just up the road! Just to get a bit more info, has the intake manifold been off the car for any reason? Are you high mileage and have never had a carbon clean?

The solenoid should be part number 037906283C. There's just one for both banks, it's located at the front of the engine just under the upper intake manifold.

[jg900rr]

Low mileage. 27k. I just picked it up from a ultra rich guy in Chicago and drove it down last week. All service was done by Audi North Shore. The last maintenance was 8/1/2020 where it indicates they 'removed the engine.' I just called them and they indicated that it was a result of a recall to the Bank 1 Cat Converter - and that they never touched the intake part of the car. There are certainly no signs of it so I have to believe them. It is just coincidental that the car has only 2k more miles on it since that service and now this. But the local Audi guys are refusing to deal with the warranty and claim I need to drive the car back to Milwaukee. So I am trying to figure it out myself. That part doesn't fit this car but I can try to find the right one. So you took the upper manifold off and just replaced the solenoid? Did you drain the coolant like the shop manual indicates? Or just removed the air pipe, PCV valve and took the cover off to access it? I've worked on the V6 but never this V8 4.2L. It is a beast!

[Ape Factory]

No need to drain coolant. Do you have a VCDS? Can you pull codes? If you want, you can drive down to my place in San Antonio. I have a VCDS and have removed the upper intake manifold quite a few times. I have a bunch of videos, some detail upper intake manifold removal, on my YouTube page. https://www.youtube.com/channel/UCrV...RoI113g/videos

May be in part 1 of the carbon cleaning video...


- - - Updated - - -

Low mileage. 27k. I just picked it up from a ultra rich guy in Chicago and drove it down last week. All service was done by Audi North Shore. The last maintenance was 8/1/2020 where it indicates they 'removed the engine.' I just called them and they indicated that it was a result of a recall to the Bank 1 Cat Converter - and that they never touched the intake part of the car. There are certainly no signs of it so I have to believe them. It is just coincidental that the car has only 2k more miles on it since that service and now this. But the local Audi guys are refusing to deal with the warranty and claim I need to drive the car back to Milwaukee. So I am trying to figure it out myself. That part doesn't fit this car but I can try to find the right one. So you took the upper manifold off and just replaced the solenoid? Did you drain the coolant like the shop manual indicates? Or just removed the air pipe, PCV valve and took the cover off to access it? I've worked on the V6 but never this V8 4.2L. It is a beast!

I pulled that part number from Audi's ETKA parts system. It's for a 2014 but should be the same for all years.

[Ape Factory]

I'm going to send you a personal message here with my email. I have something that'll help you get the car apart and back together again :)