Cone filter causing P1136 & 8 errors?
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  1. #1
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    Cone filter causing P1136 & 8 errors?

    I just rebuilt my b5.5 v6 02 Passat after a wreck and had to put in a cone filter as the metal was to warped for the OEM airbox. I am now getting errors P1136 and P1138 (too lean on both banks).

    I am assuming that this is due to the cone filter and higher air flow into the engine. Can I ignore this error? Is there a cone filter that is close to stock inflow? OR, is there a better method to handle this?

    As a side note, and I don't think this is related, but the SAI hose has not been reconnected yet -- that should not affect this, correct?

    Thanks.

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  3. #2
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    How did you mount the filter? Pics?

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    I mounted it prior to the MAF sensor with some parts from advance auto.

    Here is a picture, sorry it is night at the moment:
    conefilter.jpg

    I was assuming the MAF sensor would correct for any change in air flow, but have been reading about cone filters causing vortex instead of laminar flow which throws off the sensor. Have you heard of this?

    You cant really tell in the picture, but the PCV hose in the bottom right is broken. Could this cause a vacuum leak making it run lean, or is PCV not connected to the vacuum?

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    Moderate Moderator Steve in Chicago's Avatar
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    Are all the air path hoses intact and the joining points secure and sealed? If any air is getting sucked into the system after the MAF, it'll throw off the engine computer because it won't be accounting for that extra air.

    The flow resistance of a cone filter compared to a stock filter filter isn't going to throw off the MAF. It measures how much air is passing through it weather it be behind a clogged dirty filter or no filter at all. What may effect the MAF accuracy is air turbulence caused by something up-stream of the MAF. Did the MAF have a grid (flow straightener) on the intake side that you removed?

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    Moderate Moderator Steve in Chicago's Avatar
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    Quote Originally Posted by amw2320 View Post
    ...had to put in a cone filter as the metal was to warped for the OEM airbox.
    Use a bigger hammer.

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    The grid is still there, and everything from the MAF back is stock. All new modifications are in front of the MAF. I'll double check that hose clamps are tightened down, and follow the intake back to the engine, but I don't believe that is the problem.

    The MAF is from a salvaged vehicle, and I do have the original. I may try swapping them back out.

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    Quote Originally Posted by Steve in Chicago View Post
    Use a bigger hammer.
    Wish I could... I pulled most of it out with a 2 ton come-along so no metal was in the wheel well, but was dragging the car across the driveway. They're not joking when they say high strength steel.

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    Moderate Moderator Steve in Chicago's Avatar
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    Quote Originally Posted by amw2320 View Post
    The MAF is from a salvaged vehicle, and I do have the original. I may try swapping them back out.
    Yea. That MAF may be bad or at least filthy/contaminated.

    The open ended SAIP intake hose will not cause these problems. You may want to zip-tie a rag over the end to act as an expedient filter so nothing gets sucked into the pump.

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    Thanks for the help. One more question... I've been searching around but coming up empty -- Is there a way to test the MAF?

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    Quote Originally Posted by amw2320 View Post
    I mounted it prior to the MAF sensor with some parts from advance auto.

    Here is a picture, sorry it is night at the moment:
    Attachment 9147

    I was assuming the MAF sensor would correct for any change in air flow, but have been reading about cone filters causing vortex instead of laminar flow which throws off the sensor. Have you heard of this?

    You cant really tell in the picture, but the PCV hose in the bottom right is broken. Could this cause a vacuum leak making it run lean, or is PCV not connected to the vacuum?
    That elbow mounting to the MAF housing looks sketchy. Are you sure it's completely sealed in that spot? I can't see because it isn't a close up but normally when mounting joints together you use something like this:

    Vibrant 12700 Silicone Coupler 3" ID x 3" Long Black : Amazon.com : Automotive

    Also I wouldn't think it would be the best idea to have a elbow right there on the MAF either. Normally with any short ram there is a good foot or more between the filter and MAF and it's a straight or 180 degree bend, or the filter is directly mounted on the MAF (bad IMO).

    http://i46.photobucket.com/albums/f1...ssatIntake.jpg

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    Quote Originally Posted by amw2320 View Post
    Thanks for the help. One more question... I've been searching around but coming up empty -- Is there a way to test the MAF?
    Unplug the MAF with the car off. Turn it on and see if it runs worse.

    If it runs the same, or better, bad MAF. If it runs worse, the MAF was working and now the computer is supplying a default voltage in place of the MAF.

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    Quote Originally Posted by xerces View Post
    That elbow mounting to the MAF housing looks sketchy. Are you sure it's completely sealed in that spot? I can't see because it isn't a close up but normally when mounting joints together you use something like this:

    Vibrant 12700 Silicone Coupler 3" ID x 3" Long Black : Amazon.com : Automotive

    Also I wouldn't think it would be the best idea to have a elbow right there on the MAF either. Normally with any short ram there is a good foot or more between the filter and MAF and it's a straight or 180 degree bend, or the filter is directly mounted on the MAF (bad IMO).

    http://i46.photobucket.com/albums/f1...ssatIntake.jpg

    The elbow mounting is definitely sketchy, however I assumed that since it was in front of the MAF any leak there would be registered as flow by the sensor.

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    Quote Originally Posted by amw2320 View Post
    The elbow mounting is definitely sketchy, however I assumed that since it was in front of the MAF any leak there would be registered as flow by the sensor.
    Pre-MAF unexpected airflow is bad. Your MAF will be reading additional air coming in throwing the fuel trim off depending on how large the "leak" is. Basically you're pulling in more air then you should normally be at idle.

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    Moderate Moderator Steve in Chicago's Avatar
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    Air leaks before the MAF are inconsequential. The worst that can happen is unfiltered air is entering the system. As long as the air goes through the MAF, it gets measured. Turbulent air entering the MAF is another thing entirely and can throw off its readings.

    I'd try swapping to the original MAF to see if that helps. You can also do a flow test to see if the MAF is measuring what is expected and that the graph of the readings is smooth and consistent.

    http://www.google.com/url?q=http://w...7_F5Iw39N8AL2A

    You'll want to find out the expected 2.8 V6 MAF readings at idle and 2000 rpm and maximum flow then compare your MAF readings to those numbers.

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    Just ran a test of air flow vs RPM on VAG-COM.


    in neutral:
    AirFlowSensorGraph.jpg


    2nd gear going up hill
    AirFlowSensorGraph2.jpg

    In 2nd gear up a hill I should be hitting 152g/s at 6000 rpm and am hitting 154.

    I am assuming from this it is not a MAF sensor problem.

    Given that I am hitting what I should on the flow through the MAF sensor, would that also indicate this is not a air leak? I am starting to wonder about the fuel lines.
    Last edited by amw2320; 03-28-2013 at 09:08 AM.

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    Guess it's time to check the vacuum lines and PCV integrity. You can check your fuel readings through VCDS.

    DIY: Replacing all Vacuum Lines on 2003 B5.5 V6 (ATQ)

    17544/P1136/004406 - Fuel Trim: Bank 1 (Add): System too Lean

    Possible Solutions
    Check Mass Air Flow (MAF) Sensor
    Check Fuel Pressure Regulator
    Check Fuel Pump
    Check Intake/Exhaust System for Leaks
    Check Secondary Air Injection for Leaks
    Check Vacuum Lines for Leaks

    Special Notes
    Fuel Trim Info
    When this fault is stored and external vacuum leaks are not found, less obvious problems may be present:
    Check Evaporative Emission (EVAP) Canister Purge Regulator Valve (N80)
    Check Brake Booster and Hoses
    Check Electric Vacuum Pump ( If Applicable )
    Check Crankcase Ventilation System for faulty components. When the PCV or Crankcase Ventilation System is faulty, vacuum is typically present under the oil cap and misfire faults are common.

  18. #17
    Moderate Moderator Steve in Chicago's Avatar
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    According to those results, the MAF and it's ability to measure the air with your modified filter setup looks healthy. Did you try both sensors for the 2nd gear pull? It'd be interesting to see how those numbers compare.

    Check the trims to see how much the computer is correcting.

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    After switching to the original MAF and doing the 2nd gear pull, I have not had the check engine light back on. I've only put about 10 miles on it today so I am going to drive around a bunch tomorrow to make sure it doesn't come back. Current trim are about 6.5% on both banks for idle and 3.5% bank 1 partial and -1.5% bank 2 partial.

    If it doesn't come back I guess I picked up a bad sensor. I may throw the bad one back in again tomorrow and run the 2nd gear pull just to see what happens.

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    Hopefully the one you've got plugged in doesn't throw the code again and you're good.

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    If it was only that easy.... light came back on again. Same errors. However trim does not look too bad.

    TooLean.jpg

    From what I understand if the idle value is off it is usually a vacuum leak. However one of the RossTech pages I was reading said within +-10% was considered normal. The car is running great, I'm at a bit of a loss.

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    You can always spray carb cleaner on the vacuum lines or use a propane torch to check if you have any leaks. The more leaks fixed the better the performance.

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    You have a vacuum leak. The 10% is between 5% and -5%.

  24. #23
    Moderate Moderator Steve in Chicago's Avatar
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    I'd look for leaks too. The propane/carb cleaner trick doesn't always work so well in a car with computer controlled idle stabilization. Often times the system corrects so quickly you don't see a dramatic idle change. It's worth a shot though.

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    Thanks for the help. I'll plan on replacing all of the vacuum lines according to this DIY.

    I'm heading to Nicarauga on Monday and probably can't get parts before then, so this is going to be put off for a month.

    As I mentioned above the plastic PCV breather tube on the top front of the engine is cracked. I'm pretty sure this was not part of the vacuum, but wanted to double check.

  26. #25
    Moderate Moderator Steve in Chicago's Avatar
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    Quote Originally Posted by amw2320 View Post
    the plastic PCV breather tube on the top front of the engine is cracked.
    I'm not sure which tube you're talking about but ANY broken tubes/pipes/hoses/fittings can potentially cause a problem.

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    I'm talking about this guy.

    BrokenPCVhose.jpg

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    Moderate Moderator Steve in Chicago's Avatar
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    I'm not sure so a V6 guy will need to correct me if I'm wrong. I think that might be the air tube from the SAIPump to the drivers side combi-valve. That won't effect performance but it will get you codes for incorrect SAIP airflow.

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    It is the crankcase breather hose running from the passenger side crankcase to the PCV valve.

    By the way, thanks again for all the help and advice. As I sort of alluded to in the first post, my girlfriend totaled this car, and rebuilding it has been my first foray in car repair (so far it has only required body repair and realignment of the bank 1 camshaft). I am starting to figure out what each part/system is, but I apologise if I am not clear on some of this.

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    I have a similar setup. This may sound like a stupid question but is there a specific way the MAF has to sit? I do a second gear pull and if i press down on the accelerate quickly the car jerks forward and then goes almost like its not getting enough fuel or something. I also have no extra piping running from the MAF to cone filter. I know it sounds sketchy but after taking out my airbox i figured i'd need to figure out something until i could run some place to get the proper materials. Would i need to add extra piping after the MAF to the cone filter? Other then that the car runs fine.

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    Wish I could help. My seems to be running alright at the moment with the cracked breather hose fixed, but it usually takes awhile for that check engine light to come back on. More tubing may help you get closer to laminar air flow instead of a vortex from the cone, but everything I read about this was pretty speculative. If you aren't throwing any codes, then I would guess the MAF is working. Otherwise the O2 sensors would be yelling at you.

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