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Thread: NO Level Too High; Can't Pass Smog Check

  1. #1
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    NO Level Too High; Can't Pass Smog Check

    Just wasted $78.00 on a smog check and re-test, that I failed. Not happy. I have an '87 535i for 10 years now and it has always passed the annual smog, until now. Anyone know of an engine adjustment to lower the amount of NO level in the exhaust? I added Lucas Fuel Injector Cleaner and put in 2/3 tank of 91 octane and drove on the freeway for a half hour before the re-test. Still failed! Buying a new catalytic converter is my last resort. There has got to be a solution to this without spending a fortune??
    I read somewhere else about using Seafoam in the fuel, and even in your oil, and running it on the freeway for a couple hours before a test? Seafoam also has a 'Top Engine Cleaner and Lube' to clean out intake valves, systems, and combustion chambers. I may do that. I don't have a vacuum leak. I think the O2 sensor is good. Just had that replaced a couple years ago.
    Another possible solution is the Magnaflow Converter. It's only $100.00 on EBay. Someone in another thread said they put that Magnaflow on, and they passed.
    Any ideas here? It's December 15, and I have max until the end of January before the cops will start pulling me over for expired registration.
    Thanks.

  2. #2
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    How is the engine running overall?
    Condition/age of spark plugs along with other ignition components included in a standard tune-up?
    For 80's era vehicles I used to run to the emissions test on a quarter tank of gas or less along with a quart of isopropyl alcohol,
    along with a tune-up.

  3. #3
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    Quote Originally Posted by MIKYZZ4 View Post
    How is the engine running overall?
    Condition/age of spark plugs along with other ignition components included in a standard tune-up?
    For 80's era vehicles I used to run to the emissions test on a quarter tank of gas or less along with a quart of isopropyl alcohol,
    along with a tune-up.
    The engine runs perfect. Very smooth. Acceleration and response are top notch. Ignition and everything else are perfect. New plugs a year or so ago, I think?
    You say 'a quart of isopropyl alcohol'? That seems like A LOT! Won't that ruin the engine? How about just one of those standard size isopropyl alcohol bottles?

  4. #4
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    Back in the 80's the larger quart size was the standard size, lol.
    Don't worry, your free to dilute it further ONCE you pass the emissions test and top off at the gas station on the way home.

  5. #5
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    Search on Google "smog test chart, open images the fifth one down is chart left side of the page, I use when we have oiler cars that won't pass the smog test, it will give you a direction to go in to hopefully fix the car. Spark plugs are wr9ls as I recall are they fresh.

  6. #6
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    Quote Originally Posted by MIKYZZ4 View Post
    Back in the 80's the larger quart size was the standard size, lol.
    Don't worry, your free to dilute it further ONCE you pass the emissions test and top off at the gas station on the way home.
    So how much gas should be in the tank first?
    Should I drive it on the freeway first, or just put the alcohol in and go right to the check place?

    - - - Updated - - -

    Quote Originally Posted by jclausen View Post
    Search on Google "smog test chart, open images the fifth one down is chart left side of the page, I use when we have oiler cars that won't pass the smog test, it will give you a direction to go in to hopefully fix the car. Spark plugs are wr9ls as I recall are they fresh.
    Thanks.

  7. #7
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    1/4 tank lowest octane fuel, your usual freeway warm-up, then right before test(about a mile away) I just pour the container of alcohol into tank.
    Last edited by MIKYZZ4; 12-16-2018 at 07:31 PM.

  8. #8
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    Quote Originally Posted by MIKYZZ4 View Post
    1/4 tank lowest octane fuel, your usual freeway warm-up, then right before test(about a mile away) I just pour the container of alcohol into tank.
    My CO2, O2, CO, and HC are all within range. It's only the NO that's way out of range. The max is approx. 700-770 ppm, and mine was approx. 1100. That's a pretty substantial rise. Based on these results, my mechanic surmised it's probably the Cat.
    Are you pretty sure that might put the NO back in range?
    Will the isopropyl alcohol throw the other ranges off?
    I've also heard that a fluid called Sea Foam in the tank right before the test may also help? Not sure which method I want to use? My mechanic said he knows of an 'unlimited re-test' place, and this may take a couple more tried before I get it right. It's maddening, because I've already paid for a test AND re-test to no avail. Sucks.
    Thanks for the tip.
    I'll keep you posted. Hope it's good news.
    Last edited by Hypnotized; 12-17-2018 at 05:47 PM.

  9. #9
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    With those type of readings I would focus on intake leaks or failed converter.

  10. #10
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    No Level Too High; Can't Pass Smog Check

    As an off the wall consideration(s), as NO is generally caused by combustion temps (lean condition) and high compression, I would look at:
    1) cylinder soak - breaks up carbon and restores compression
    2) fuel trims - if they are high idle and drop with load/rpm then likely a vacuum leak
    3) fuel pressure - if you have a low pressure then the system will be lean. You could still run without issue but be slightly lean. Will also have high trims overall

    The cats might still need replacement, but you would likely have higher HC as well (or at least upper end of range).

    Edit: might be hard to check trims, I was thinking 97... not 87.

    2001 750iL DD74441
    Stock

    RIP: 2003 540iA Sport GS56111
    H&R front springs, Ultimate Cup Holder, Euro Dash & Armrest, Grom, BavSound Stage1
    Last edited by TheAngryBear; 12-17-2018 at 06:35 PM.

  11. #11
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    Thanks to MIKYZZ4
    .
    Last edited by Hypnotized; 12-17-2018 at 09:57 PM.

  12. #12
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    Quote Originally Posted by TheAngryBear View Post
    As an off the wall consideration(s), as NO is generally caused by combustion temps (lean condition) and high compression, I would look at:
    1) cylinder soak - breaks up carbon and restores compression
    2) fuel trims - if they are high idle and drop with load/rpm then likely a vacuum leak
    3) fuel pressure - if you have a low pressure then the system will be lean. You could still run without issue but be slightly lean. Will also have high trims overall

    The cats might still need replacement, but you would likely have higher HC as well (or at least upper end of range).

    Edit: might be hard to check trims, I was thinking 97... not 87.
    I printed your answer out and taking it to my mechanic. He's on my side and wants to assist with my passing that test.
    Thanks.
    Last edited by Hypnotized; 12-18-2018 at 11:29 AM.

  13. #13
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    Have you cleaned the throttle body yet, if is gummed up it won't idle right

  14. #14
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    I second the isopropyl alcohol comment. Also, if you are waiting in line for the emissions test, your catalytic converter can cool off too much. Put the car in neutral and keep the rpm up at 2500 can help heat the cat.

    Consider disconnecting the exhaust before the cat matrix and examining it for breakdown? You might need a camera if it is around a bend and out of sight.

    There is only so much you can do to help an old cat...

    Sent from my LG-H915 using Tapatalk


  15. #15
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    I first posted this issue on December 15, 2018. It's now June 2, 2019. I finally resolved this issue. Turns out it was the last thing you want it to be. It was the cat! I ended up purchasing a new one after attempting every solution suggested in this thread and nothing worked. It was the old cat. After it was installed, I went for a drive on the freeway for about 15 miles and pulled right in to my smog check place, and it passed! Finally!! It was only the NO out of range, and I needed a new catalytic converter.
    Thank you to everyone!!

    - - - Updated - - -

    Quote Originally Posted by TheAngryBear View Post
    As an off the wall consideration(s), as NO is generally caused by combustion temps (lean condition) and high compression, I would look at:
    1) cylinder soak - breaks up carbon and restores compression
    2) fuel trims - if they are high idle and drop with load/rpm then likely a vacuum leak
    3) fuel pressure - if you have a low pressure then the system will be lean. You could still run without issue but be slightly lean. Will also have high trims overall

    The cats might still need replacement, but you would likely have higher HC as well (or at least upper end of range).

    Edit: might be hard to check trims, I was thinking 97... not 87.

    2001 750iL DD74441
    Stock

    RIP: 2003 540iA Sport GS56111
    H&R front springs, Ultimate Cup Holder, Euro Dash & Armrest, Grom, BavSound Stage1
    Issue finally resolved!! It was the old catalytic converter that was the issue, after trying everything else. Finally bought a new one, had it installed, and it passed with flying colors.
    Thanks for your help.

    - - - Updated - - -

    Quote Originally Posted by MIKYZZ4 View Post
    With those type of readings I would focus on intake leaks or failed converter.
    Issue finally resolved. It needed a new cat.
    Thanks for your assistance.

  16. #16
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    Was hoping otherwise but at least you got it corrected.
    And thanks for the follow up!!!


    2001 750iL DD74441
    Stock

    RIP: 2003 540iA Sport GS56111
    H&R front springs, Ultimate Cup Holder, Euro Dash & Armrest, Grom, BavSound Stage1

  17. #17
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    Quote Originally Posted by TheAngryBear View Post
    Was hoping otherwise but at least you got it corrected.
    And thanks for the follow up!!!


    2001 750iL DD74441
    Stock

    RIP: 2003 540iA Sport GS56111
    H&R front springs, Ultimate Cup Holder, Euro Dash & Armrest, Grom, BavSound Stage1
    Yes, sir! Thank you.

  18. #18
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    Unfortunately a new cat was required, glad issue was solved.
    Thanks for the update!

  19. #19
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    Quote Originally Posted by MIKYZZ4 View Post
    Unfortunately a new cat was required, glad issue was solved.
    Thanks for the update!
    Yes, sir! Thanks for your help. What a relief to finally pass the smog check and get my registration.

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