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Thread: Emissions Error and Secondary Air Pump Setup Troubleshooting.

  1. #1
    Registered User Aronis's Avatar
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    Emissions Error and Secondary Air Pump Setup Troubleshooting.

    Ok all first a disclaimer: Those who deleted their secondary air pump system please chime in with knowledge but I am not going to remove mine.

    My last issue since my rebuild has been an error with the secondary air pump system. I have tried doing the usual trouble shooting and have not found the answer.

    My mechanic suspects a leak in the vacuum system on a seal that sits between the brake master cylinder and the firewall.

    What happens is than when I start the car the secondary air pump runs quite loudly. If I wait until it stops I do not get a CEL, but if I don't wait I get a CEL and the scan below. I replaced the solenoid and the actual secondary air pump and that did not fix the problem.

    What we suspect is that when the car is being driven before the pump shuts down the vacuum is being use for other things and as a result there is not quite enough to open the combi-valves fully and I get the error. We suspect the combi-valves are only opening slightly, just enough to inject air into the exhaust for it's usual purpose, but not enough for efficient use of the flow and thus the pump sounds much louder. I am considering applying vacuum to the combi-valve with a syringe to see if the sound is different. Too bad the combi-valves are so hard to get at to remove and actually examine.

    There is an associated error message about "Brake Boost Vacuum System" but the brakes feel fine.

    We tried to make the secondary air pump run the test (block 77 if I recall) which is done by reving the engine to 2500 to 2600 RPM and holding the brake at the same time but the test wound not run on either bank.

    I did the brake test for vacuum and that gave a correct reading.

    The exhaust temp sensor thing is very intermittent especially since I did the re-solder thing.

    So any input?

    Thank you,

    Mike

    PS it's nice having A/C once again.


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    '18 BMW M5, '19 Porsche Boxster GTS
    (prior '94 325is, '97 M3, '00 A6 4.2,'03 RS6,'08 A4 Cab,'13 A8L,'15 Q7,'16 BMW M2,

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    Silly question, but - do you actually want to fix the problem or just shut down the light?

    If it's the former - properly inspect the whole N112/N249 vacuum system (it's actually a separate one from brakes).
    There's a vacuum line on driver's side, routed near the PS reservoir. It goes from the fenderwell-mounted vacuum reservoir to the N249 (DV control) valve plumbing. If you let the car sit for a while, then disconnect the line - will it let the air in? I.e. will it produce a noticeable hissing sound?

    If not - it's either one of the lines or check valve being at fault.
    When driving off you pressurize (boost) the intake - and there's no more vacuum to keep combi valves open.

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    Registered User Aronis's Avatar
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    Nubcake, Thanks for the input. I have looked at the entire vacuum setup from the reservoir to the combi-valves and cannot find a fault. When I disconnected the line to the control solenoid there was plenty of vacuum on the vacuum side.

    I am not so sure about there no longer being vacuum after you drive off. The brakes depend on a supply of vacuum to 'assist' you when you push the peddle. I don't think the brakes rely on a 'reserve' of vacuum created in the few minutes of idle when you start your car LOL.

    Shut down the light would be fine.....'code it out' I guess? I kind of want to find the problem since I don't want the brakes to give out suddenly.

    Mike
    '18 BMW M5, '19 Porsche Boxster GTS
    (prior '94 325is, '97 M3, '00 A6 4.2,'03 RS6,'08 A4 Cab,'13 A8L,'15 Q7,'16 BMW M2,

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    I think your theory about the combi valves not opening enough is valid. Do you have a Mityvac? you could use that to apply vacuum up at the solenoid under the engine cover. I think you previously mentioned you replaced that solenoid already, but you could try applying vacuum up there and see if the pump quiets down. That would back-up your theory of low vacuum.

    I think the P1479 code is the key issue. You mention that the VAGCOM test passed, but I suspect the test passed because you were just sitting idle when you ran it. Like the air injection issue, it's OK if you aren't driving. That seems to point to a slow leak or weak booster pump.

    First, I'd suggest a google search for CEL P1479, there are quite a few threads about the issue out there. Most seem to point at a vacuum leak or brake booster pump failure. I agree with nubcake that you need to check all the various vacuum lines and valves. The google threads describe what a lot of people look at as well. You mentioned your mechanic suspected a specific leak, has he tried to fix it?

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    Registered User Aronis's Avatar
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    GreggPDX, we discussed the approach to that possible leak. It sounds like a few hours work and it may come to that kind of trial and error approach. The seal he was referring to is just an O ring.

    I'll read up on CEL P1479.

    Thank you,

    Mike
    '18 BMW M5, '19 Porsche Boxster GTS
    (prior '94 325is, '97 M3, '00 A6 4.2,'03 RS6,'08 A4 Cab,'13 A8L,'15 Q7,'16 BMW M2,

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    Registered User Aronis's Avatar
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    One thread ended up being a bad Suction Jet Pump which I replaced with a new one, but under my theory of a hell a new part can be bad, I hope it is not that. That Suction Jet Pump is a PITA to get to on the RS6. You have to remove the intake completely.

    Mike
    '18 BMW M5, '19 Porsche Boxster GTS
    (prior '94 325is, '97 M3, '00 A6 4.2,'03 RS6,'08 A4 Cab,'13 A8L,'15 Q7,'16 BMW M2,

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    SJP is exactly the reason why you get vacuum for brakes even under boost.
    N249/N112 system is however connected directly to the manifold via a checkvalve.

    Actually I haven't looked at the system for a long time now (and on top of that have a euro spec car in mind), so I might be mistaken. But it really makes perfect sense to me.
    Re: just shutting off the diagnosis - if you decide to go this route, I'm going to need a readout of your current flash. This can get it. PM me if you need further assistance with this.

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    Registered User Aronis's Avatar
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    I went to get my car inspected today and it failed. At my milage I am allowed one "red" light on their scanner, but I have two linked issues which will not set to the "readiness." Those are the secondary air pump and the catalytic converters. I was told they are linked so if the first fails the second will also. I was able to get the EVAP to go to readiness.

    So I took the intake off and inspected again. All the tubing is fine. I made a vacuum attachment so I could apply vacuum to the comb-valves directly and try to blow into the fitting by mouth.

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    I wanted to quantify this better so I set up a pressure gauge and used my compressor to blow air in the combi-valve while my shop vac applied the vacuum. No flow into the combi-valves. I think they are both shot.

    The car was cooled down a bit by the time I put it all back together but not cool enough to trigger the secondary air pump to run. I tried using VAG to trigger the "test" on block 77, and this time I was able to make the car rev to 2500 while depressing the brake but the test would not start.

    I am going to let the car cool down overnight and start it up to see if the pump runs. I hit the comb-valves with a wrench a few times> Stuck or diaphragm gone, not sure. I could put an Allen Wrench on 4 of 4 on the driver's side but only 3 of 4 on the passenger side. I spoke with my mechanic and he is confident he can change both without dropping the engine.

    I had the Combi-valves on my parts list last years. Should have done it. DAM IT! What 's another $600 in parts!

    Mike
    '18 BMW M5, '19 Porsche Boxster GTS
    (prior '94 325is, '97 M3, '00 A6 4.2,'03 RS6,'08 A4 Cab,'13 A8L,'15 Q7,'16 BMW M2,

  9. #9
    Registered User AndyRS6's Avatar
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    I used this combination
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    Work for me


    Andriy

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    And there are only 3 bolts on passenger sideClick image for larger version. 

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    Andriy

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    Or are you talking about this one?Click image for larger version. 

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    Andriy

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    One the passenger side there is one on the back I think that I could not get an Allen on. Are you saying the one in front is the only bolt on the bottom of it? That would be very nice! LOL


    I have a similar cut off allen. LOL. They come in very hand. So is there only one on that side?

    Mike
    '18 BMW M5, '19 Porsche Boxster GTS
    (prior '94 325is, '97 M3, '00 A6 4.2,'03 RS6,'08 A4 Cab,'13 A8L,'15 Q7,'16 BMW M2,

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    From my last service (cam tensioners). I can see one bolt in front. I am looking for a better photo. But if there is just one bolt, I can DIY.

    Mike
    '18 BMW M5, '19 Porsche Boxster GTS
    (prior '94 325is, '97 M3, '00 A6 4.2,'03 RS6,'08 A4 Cab,'13 A8L,'15 Q7,'16 BMW M2,

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    Andriy

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    Registered User Aronis's Avatar
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    I see the bolts you are pointing to. Are you saying THOSE are the ones to remove instead of those directly on the bottom of the combi-valves? They look easier to get a wrench on.

    It's funny I took a bunch of photos but did not really realized I should have taken more various subsystems up close. The passenger side is hidden behind a pair of metal tubes on my photos.

    So if I remove these bolts and the other two on the back of the combivalve does the valve and the mount come out easily? Are there seals needed?

    Mike
    '18 BMW M5, '19 Porsche Boxster GTS
    (prior '94 325is, '97 M3, '00 A6 4.2,'03 RS6,'08 A4 Cab,'13 A8L,'15 Q7,'16 BMW M2,

  16. #16
    Registered User Aronis's Avatar
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    PS I am pricing parts. Combivalve for 4.2 L v8 - $170, Combivalve for RS6 $270. WTF? How different could they be? bastards.

    Mike
    '18 BMW M5, '19 Porsche Boxster GTS
    (prior '94 325is, '97 M3, '00 A6 4.2,'03 RS6,'08 A4 Cab,'13 A8L,'15 Q7,'16 BMW M2,

  17. #17
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    Quote Originally Posted by Aronis View Post
    PS I am pricing parts. Combivalve for 4.2 L v8 - $170, Combivalve for RS6 $270. WTF? How different could they be? bastards.

    Mike
    Are used ones out of consideration, if I may ask?
    A lot of people delete those...

  18. #18
    Registered User AndyRS6's Avatar
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    Quote Originally Posted by Aronis View Post
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    I see the bolts you are pointing to. Are you saying THOSE are the ones to remove instead of those directly on the bottom of the combi-valves? They look easier to get a wrench on.

    It's funny I took a bunch of photos but did not really realized I should have taken more various subsystems up close. The passenger side is hidden behind a pair of metal tubes on my photos.

    So if I remove these bolts and the other two on the back of the combivalve does the valve and the mount come out easily? Are there seals needed?

    Mike
    I remove combi valve with mount because I need more room. In your case I think would be better to remove combi valves only, but still you need to loosen all three bolts on passenger side to have enough clearance for one forward dolt on combi valve.
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    You need paper gasket between cylinder head and combi valve mount ( 078131120M pass. 078131120E driver) and 4 metal for combi valve ( 078131120K )

    Before you remove combi I would recommend to use brake fluid vacuum pump few times to see from inlet side if valve opens ( applied vacuum more than one time)
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    Also did you check pump it self with hose removed to combi ( how loud it work)?




    Andriy

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