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Thread: E36 325is Emissions Help Needed - High HC

  1. #1
    Join Date
    Aug 2005
    Location
    Denver, CO
    Posts
    46
    My Cars
    1994 BMW 325is

    E36 325is Emissions Help Needed - High HC

    Hello community!

    I just recently moved to Colorado where I now live in a county that requires emissions testing. Unfortunately my 1994 325is (M50) OBD1 autocross/track car has failed the test today. Here are the details on my car:

    - 215k miles
    - Stock engine with stock chip
    - New Spark Plugs, NGK BKR6EK, only 500 miles ago
    - New spark plug ignition coils, 1500 miles ago
    - New Bosch oxygen sensor less than 1000 miles ago
    - Air filter is relatively new
    - Oil change 500 miles ago
    - New fuel injectors about 2000 miles ago
    - New fuel pump about 100 miles ago
    - New fuel filter about 100 miles ago
    - New MAF 2000 miles ago
    - Cat replaced about 25k miles ago
    - Stock DME chip

    Before heading to the emissions test, I ran the car hard on the interstate for about 30 minutes to make sure that the cat was nice and hot. The emissions test is on a dyno and includes speeds through 1st, 2nd and 3rd gear up to 60 mph. Here are the results from the test (units are grams per mile):

    Category / Reading / Limit
    HC / 3.0037 / 1.2000
    CO / 12.497 / 15.0000
    NOx / 3.037 / 3.0000

    So as you can see, it failed the HC quite badly while just barely failing the NOx. I think a high HC means that it's running rich but correct me if I'm wrong.

    I've check for vacuum leaks and such and don't see anything. Where should I be focusing my efforts? Thanks!
    Last edited by Smorgousford; 07-11-2018 at 06:18 PM.

  2. #2
    Join Date
    Jun 2010
    Location
    NY
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    9,079
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    1997 328i
    Two things left to do, a new set of coils and to properly smoke test the vacuum system.

    Here is a new set from ebay, I think you have the 4 bolt coils?
    https://www.ebay.com/itm/OEM-Quality...i/282778888787
    Attn. NEWBIES: Use the search feature, 98% has already been discussed.
    Click the search button, select "search single content type", select the "e36 sub forum" specifically, try the "search titles" then try the "search entire posts".

  3. #3
    Join Date
    Aug 2005
    Location
    Denver, CO
    Posts
    46
    My Cars
    1994 BMW 325is
    Quote Originally Posted by Eric93se View Post
    Two things left to do, a new set of coils and to properly smoke test the vacuum system.

    Here is a new set from ebay, I think you have the 4 bolt coils?
    https://www.ebay.com/itm/OEM-Quality...i/282778888787
    Forgot to mention that I did the spark plug ignition coils about 1500 miles ago.

    Do you have a good link to the proper way to smoke test an E36? I've looked around and haven't been able to find a test with a full description.

  4. #4
    Join Date
    Aug 2009
    Location
    sunnyvale CA
    Posts
    1,589
    My Cars
    325is
    So how does it work? The readings are for the worst range?
    no known rpm the engine is at?

    1st, 2nd and 3rd gear up to 60 mph.

    Category / Reading / Limit
    HC / 3.0037 / 1.2000
    CO / 12.497 / 15.0000
    NOx / 3.037 / 3.0000

    CA was bad because we did 2 speeds but this could be worse. I cant compare to out test values we do % and PPM
    And they have no been lowered for a 20 year old car.




    Without the other values we can only guess what to replace

    You have done the most common but the smoke test for vacuum system leaks
    The car is high miles so worn pars is possible.
    Carbon buildup treatment if you believe Sea foam etc works
    Do you lose any oil?

    Do you detect any miss fires? You have to exercise the VANOS system @3000 rpm to reach 60 so it may have problems there.

    Did you fail CO with a lower limit number?
    Attached Images Attached Images
    Last edited by gc325is; 07-11-2018 at 11:06 PM.

  5. #5
    Join Date
    Dec 2013
    Location
    Chicagoland area
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    4,372
    My Cars
    EXOTICS
    Have a shop perform an intake smoke test,
    with a professional smoke machine,
    that can inject a correct and continuous psi.

  6. #6
    Join Date
    Dec 2013
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    Chicagoland area
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    EXOTICS
    But for those that insist on DIY,
    even though results are questionable,
    here is one that has served me well:
    https://www.youtube.com/watch?v=AsgB9eBl58I

    I also tape glove to intake after removing MAF,
    my modification being; taping base of glove around intake boot opening,
    then cutting tip off of single finger on glove,
    followed by inserting hose in that opening - then applying tape securing opening to hose.

  7. #7
    Join Date
    Mar 2014
    Location
    UTC-5:00
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    568
    My Cars
    X5, R90/6
    High HC is usually from running lean. Not enough fuel or usually too much air. Poor man's smoke test is spray a can of starter fluid (ether) on your vacuum lines & hoses. When the RPMs change you found a leak. Do you have an airport near you? Usually they sell MOGAS or E0 92/3 Octane (e0 means no ethanol) fuel. Same as premium pump gas just without the corn alcohol in it. It'll run a bit better. Run down to empty, spend the money to in 1/4 tank of E0 mogas (this is fine with cat converters) then drive for a bit and get it hot. Fix the air leaks and it should be fine on pump gas. Fix the air leaks and if you still have an issue try it on AV/mogas. If it passes on mogas find out why it failed and look for a fix --or sell the car. If it fails with no air leaks and mogas then idk maybe look at rings?? Run thicker oil? idk... Valve stems? No idea but something is not right.

  8. #8
    Join Date
    Jan 2016
    Location
    Ca
    Posts
    6,981
    My Cars
    2001 525it
    Search smog check chart, look at images follow the left side of the page down about 11 images there you will find this handy chart on what to repair for when you fail
    Last edited by jclausen; 07-12-2018 at 01:45 AM.

  9. #9
    Join Date
    Aug 2009
    Location
    sunnyvale CA
    Posts
    1,589
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    325is
    here is another chart with burn curves

    note HC can be high in a lean or rich condition but the O2 and CO are different. This does not show how a CAT may alter the burn curve.



    Last edited by gc325is; 07-14-2018 at 11:01 AM.

  10. #10
    Join Date
    Jan 2016
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    Ca
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    2001 525it
    My recommended chart is much less complicated

  11. #11
    Join Date
    Jun 2010
    Location
    NY
    Posts
    9,079
    My Cars
    1997 328i
    You could also have leaking injectors, did you do anything with them lol?

    For some a bottle of CRC GTP is all it takes to get over the last hump, but you sound like your trying to be thorough. Put premium gas and the bottle of CRC GTP and drive it for 100 miles before testing, drive it hard a few times (hit redline).
    Attn. NEWBIES: Use the search feature, 98% has already been discussed.
    Click the search button, select "search single content type", select the "e36 sub forum" specifically, try the "search titles" then try the "search entire posts".

  12. #12
    Join Date
    Aug 2005
    Location
    Denver, CO
    Posts
    46
    My Cars
    1994 BMW 325is
    So the problem was that the cat that the previous owner had installed was apparently faulty. I just installed a new Bosal catalytic converter exhaust section from Rock Auto and got the following passing numbers:

    Category / Reading / Limit
    HC / 0.7891 / 1.2000
    CO / 1.7131 / 15.0000
    NOx / 0.0187 / 3.0000

    What a huge difference working cats makes!

  13. #13
    Join Date
    Aug 2009
    Location
    sunnyvale CA
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    325is
    The old CAT was killed when when the HC remained too high. The new one may have the same ending if the other fixes did not work. Cheap CATs also wear out faster than OEM but cost $1000s

    Do you notice more power or less gas mileage now?


    jclausen My recommended chart is much less complicated Search smog check chart, look at images follow the left side of the page down about 11 image .... LOL You must have a great Search engines. Time for some more cookies.

  14. #14
    Join Date
    Oct 2004
    Location
    Aliso Viejo, CA
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    679
    My Cars
    '97 328i '73 Porsche
    Little late to the party, but I just saw this post. If the car was running well, idling well, with no MIL codes, with the mileage on the car the cats was going to be my first guess. I have a 1997 328i with 206K miles, and I've been barely passing on HC for the past several smog checks. Although I have an OBDI manifold and M3 cams, I can still pass CA smog when I map the ECU back to stock, and reinstall the stock air cleaner. I have been shopping around for replacement cats, and when I need to replace, I plan to get the CA Magnaflow retrofit for $716:
    https://www.ebay.com/itm/1996-1998-B...53.m1438.l2649

    Someone had suggested the cheap chinese coils as a possible solution to a high HC problem. New coils may help, but be careful of the cheap aftermarket ones. I tried those once, and they seemed to have a short term improvement on HC, and helped me to pass smog once, when HC was high. I also ran the car hard right before pulling it into the testing bay. I honestly think that the hot cats made the difference, not the cheap chinese coils. If I would have installed the coils and never removed them again, they may have been okay, but after any length of time, when you remove them, they break apart. After removing and replacing once, I had a misfire and threw away the chinese crap and reinstalled my original coils. So glad I saved them. I am still running them after 206K miles, and no problems. If I ever need to replace one or more coils, I will replace them with factory coils, or buy quality aftermarket coils.

    I love the E36 model and I have had mine for 15 years. Good luck with your car and hope this helps!
    Alpine White '97 328i 5 speed: S50 cams, M50 Manifold, TMS Cam/Intake Specific Software, UUC Stage II Clutch Kit, EVO 3 Short Shift Kit with DSSR, CAI, Cat-Back, ASC, Fan & CDV Delete, All M3 Stock Suspension & Brakes, 3.23 LSD, 17" DS II's, Stainless Steel Brake Lines & Clutch Line, Depos Elipsoids & M3 mirrors

  15. #15
    Join Date
    Oct 2016
    Location
    Tenerife, Spain
    Posts
    628
    My Cars
    1997 BMW E36 323i
    To prevent damaging your new catalytic convertor: make sure the fuel pressure regulator is good. I'm about to replace mine because it doesn't drop pressure at high intake manifold vacuum (at idle and low loads). Also check the vacuum hose between manifold and FPR. If that's leaking, then you'll have both a vacuum leak AND a malfunctioning FPR (which needs the vacuum to lower pressure at idle and low loads)..
    You can test with a fuel pressure tester: it should be 3.5 bar with vacuum hose disconnected (or at higher loads), and 2.8 bar at idle with vacuum hose connected.

    I think I've been burning through two (or even three) catalytic converters the past 3 years due to the bad FPR.. The DME can't properly adjust to a bad FPR and mixture will often be bad at all loads and rpm's.


    1997 E36 BMW 323i
    (European) 275k km (171k miles), with following small mods:

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