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    Calif Smog Test Question

    When I bought my car 2 years ago, the Smog Check showed that the NO (Nitrogen Oxide) levels were high - right near the limit, but the car passed.

    Now, 8,000 miles later, I'm due for a retest and was wondering what I could do to lower the levels of Nitrogen Oxide.
    sigpic
    1988 5 spd.Cabrio/Lachs Silber/Black Leather/123k/Dealer Serviced & Maintained by both PO's
    Clarion DXZ785USB HU, BBS Wheels, Leather e-brake handle & e-brake boot, Mtech 1 Wheel, Maplight Mirror, Performance chip, Rear Headrests.
    Previous E30: 1986 5 spd. 325es/Delphin Gray/Black Leather/191k









    #2
    New Cat.

    Comment


      #3
      Originally posted by Danny View Post
      New Cat.
      True - very likely. But I like to refer to that as "plan b". Before taking the car in for the sniff test, do the following.....

      Change engine oil & filter

      If you have a performance chip in the ECU, re-install the stock chip

      Check your 02 sensor - it may need to be replaced if its been in use for a while. FYI - there are two versions (3-wire & 4-wire) - make sure you get the correct replacement if you change this out

      Run 87 octane fuel

      Buy a bottle of CRC brand "Guaranteed To Pass" - follow the directions exactly!

      You might want to try using a technique called SeaFoam. There's a lot of information about this process on this site, just do a search. I did all of the above and have been able to pass the smog test with a catalyst converter which had many, many years of use on it.

      Hope this helps.

      Jon
      Rides...
      1991 325i - sold :(
      2004 2WD Frontier King Cab

      RIP #17 Jules Bianchi

      Comment


        #4
        Originally posted by Jon325i View Post
        Run 87 octane fuel
        Why 87?

        Wouldn't 91 do better?

        Comment


          #5
          Drive the shit out of it for the 30 minutes before you test and don't wait around and let it sit at all before they hook it up. If they have you waiting, drive around the block a few times. Get that cat nice and hot.
          sigpic
          "The best argument against democracy is a five-minute conversation with the average voter." - Winston Churchill

          Comment


            #6
            Originally posted by Danny View Post
            Why 87?

            Wouldn't 91 do better?
            Higher octane grade fuels burn hotter - this can effect the emissions readings at test time. You want the catalyst to be super hot when you test it.
            Rides...
            1991 325i - sold :(
            2004 2WD Frontier King Cab

            RIP #17 Jules Bianchi

            Comment


              #7
              Originally posted by Jon325i View Post
              Higher octane grade fuels burn hotter - this can effect the emissions readings at test time. You want the catalyst to be super hot when you test it.

              So wouldn't 91 be better?

              Comment


                #8
                make an adjustment to the afm to make it run slightly richer mix.

                I recently just passed smog after the first test when my NO was at 2600. Changing the mix brought me down to 200 which is way under the 760 limit. It also didn't effect the CO enough to make me fail that just don't make it too rich.
                Originally posted by Hawt drift chick
                Yeah, i'm a good dude i swear, i just like to be balls to the wall.

                Comment


                  #9
                  Originally posted by Jon325i View Post
                  Higher octane grade fuels burn hotter - this can effect the emissions readings at test time. You want the catalyst to be super hot when you test it.
                  I think you contradicted yourself...

                  and higher octane fuel burns cooler iirc
                  1989 cirrisblau-metallic 325i

                  Comment


                    #10
                    NOX is caused by the car running hot, if you want the nox to be lower make sure that the thermostat and aux fan are in proper working order. if they are not cooling the engine properly the nox levels will be high. try to go on a cooler day if that is possible

                    Comment


                      #11
                      Damn, now I'm confused. Hot? Cold?
                      BTW, how do I adjust the AFM to make it run richer and how much is too much?
                      I'm going to get the CRC additive and swap out my chip for the stock one, but should I run 91 Octane?
                      Bring it to the shop Hot or Cold?
                      Thanks.
                      sigpic
                      1988 5 spd.Cabrio/Lachs Silber/Black Leather/123k/Dealer Serviced & Maintained by both PO's
                      Clarion DXZ785USB HU, BBS Wheels, Leather e-brake handle & e-brake boot, Mtech 1 Wheel, Maplight Mirror, Performance chip, Rear Headrests.
                      Previous E30: 1986 5 spd. 325es/Delphin Gray/Black Leather/191k








                      Comment


                        #12
                        normal operating temperature, make sure it doesn't run hot

                        Comment


                          #13
                          DO NOT mess with the AFM unless you can set it properly with some sort of emissions reading tools... It has to be adjusted with the o2 sensor off and then you have to watch the air-to-fuel ratio as you adjust. This is not something you just tweak a lil bit.

                          "BMW Style 32 Poster-Child"
                          HTTP://WWW.CLAVINZERO.COM/e30-5-lug
                          **(My Guide to E36 M3/Z3 1.9L 5-lug Swap)
                          **

                          Comment


                            #14
                            Originally posted by FLUTE007 View Post
                            normal operating temperature, make sure it doesn't run hot
                            My Fan CLutch might be going bad because if I let the car idle for several minutes on a hot day, like 90+, the temp needle will move a little above the halfway mark.

                            It's supposed to cool down this week, so I will probably drop the car off at the smog place because it's near work, walk to work, have them smog it and hope it passes.

                            I'm going to change the plugs and oil and oil and air filters, plus run the CRC additive.

                            So I should have them smog it when the car is cold if my NO levels are high?

                            And Premium or Regular? I still need to swap my chip as well.
                            sigpic
                            1988 5 spd.Cabrio/Lachs Silber/Black Leather/123k/Dealer Serviced & Maintained by both PO's
                            Clarion DXZ785USB HU, BBS Wheels, Leather e-brake handle & e-brake boot, Mtech 1 Wheel, Maplight Mirror, Performance chip, Rear Headrests.
                            Previous E30: 1986 5 spd. 325es/Delphin Gray/Black Leather/191k








                            Comment


                              #15
                              Originally posted by shiftbmw View Post
                              Drive the shit out of it for the 30 minutes before you test and don't wait around and let it sit at all before they hook it up. If they have you waiting, drive around the block a few times. Get that cat nice and hot.
                              Exactly! This works like a charm.
                              tasty

                              Comment

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