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1986 Euro 525e Failing Nox Test on Emissions

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    1986 Euro 525e Failing Nox Test on Emissions

    I know it is not an e30, but it does have an ETA motor so I was hoping you guys could provide me with some insight or some personal experience.

    I just purchased a 1986 Euro 525e and have been struggling to get it to pass emissions. I will start off with the scores, and then explain what I have done so far.

    25/25 Test
    Reading Allowed
    HC 12 157
    CO % 0.01 1.00
    NOx 2277 1121

    50/15 Test
    Reading Allowed
    HC 12 162
    CO % 0.01 0.91
    NOx 2421 1227

    I have read every thread in here that I could find with various suggestions on what the issues could be, as well as little tips to help it pass. I am down to 6 days to get it to pass before I can no longer legally drive the car, as I was out of town for a week and a half after I purchased it. The car runs well, and runs cool as far as the water temp goes, however the high NOx is pointing towards it running lean.

    I found and fixed a vacuum leak, tested the O2 sensor, and while it appears to be working (Varying voltage) it may be malfunctioning. I am going to replace the 02 sensor ASAP, as it is a single wire so relatively cheap. Per a bad recommendation, I did replace the catalytic converter against my gut feeling, and it made 0 difference, so that is not the issue either. Plug wires appear to be in good shape, as well as the plugs. I do not believe the car has an EGR valve.

    Any further tips or suggestions would be great, or if you need more information please let me know. I have done tests after fixing the vacuum leak, as well as the new cat, and neither of those were the issue, nor did they make a significant difference. Thanks in advance!



    #2
    High NOx is indicative of excessive cylinder temps....are they the right plugs, try one heat range lower. Lean air/fuel, hole in the exhaust....
    -03/2005 E46 330D Touring 6spd(204hp/410nM) Sapphire Black/Naturbraun Sport...300k KM & 35mpg(mixed)

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      #3
      Originally posted by MikeDE View Post
      High NOx is indicative of excessive cylinder temps....are they the right plugs, try one heat range lower. Lean air/fuel, hole in the exhaust....
      I am thinking it may be a lean/air fuel. There are no holes in the exhaust, and I will double check the plugs.


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