High NOx(smog help)

Discussion in '2.3L (N/A & Turbo) Tech' started by slo90notchback, Oct 20, 2011.

  1. I took my car to get a smog check done and it failed the No(ppm) of the test. The guy at the shop told me If i wanted it to pass that I needed to replace the catalytic converter but I read on another website that high NOx numbers happen when the egr valve is not working properly. I only have one free retest so do I replace the cat and clean the egr?

    Results for the emissions test


    Result Fail
  2. I would clean the EGR and possibly replace the O2 Sensor as well.

    Good luck,

  3. High NOX forms when the mixture burns too hot. The EGR helps reduce combustion temperatures under certain conditions, so it could be involved. But there are other things that can cause high NOX. If you have excessive carbon build up in the cylinders, you NOX will be high, or if your engine is leaning out due to a plugged fuel filter, vacuum leak, plugged injector(s), wrong spark plugs, incorrect timing, etc. There are lots of things that can cause high NOX. And yes the cat can be involved, though cats don't fail on their own, they are destroyed by incorrect tuning or overheating.
  4. Can removing the spout connector gaurantee I pass smog this time while I fix the issues the car has? I only have a week to get the car smogged and it is only one free retest.
  5. Dump some acetone in the gas tank - about 15 ounces - from what i understand it mixes with the gas and allows it to burn more complete reducing emissions significantly.

    Dump some in and drive it around a bit to get it good and mixed and in the fuel before you test.

    last time we had emission testing in Florida my 81 280zx turbo failed (this was over ten years ago) - (my cat was gutted) and I was told to dump acetone in the tank and get it good and mixed in the fuel and engine nice and warm. Went thru and passed with no problems.
  6. Im trying to make the car pass legally :D. I will be replacing the catalytic converter tomorrow. I cleaned out the egr and it was somewhat dirty. I reviewed the smog test and it appears to show my timing to be at 15* but he did not fail me. What is the stock ignition timing supposed to be at on these motors? I tallked to the exhaust shop and they said the car had an old style cat which was illegal now:shrug:. They also said 90% it is the cat that has failed and he is certain replacing it will make my car pass.

    Here are the rest of the results on the test.
    Test 15mph
    Rpm 1754
    %CO2 meas; 14.8
    %02 meas; 0.0
    Hc(ppm) max: 86 meas:37
    Co(%) max: 0.54 meas;0.02
    NO(ppm) max:565 meas:660

    Test 25mph
    Rpm 1714
    %CO2 meas; 14.8
    %02 meas; 0.0
    Hc(ppm) max: 67 meas:28
    Co(%) max: 0.45 meas: 0.02
    NO(ppm) max:522 meas:539
    Results fail
  7. I hear ya on the "legal" part, but in fairness the test is skewed because you are now more than likely not burning the fuel that was originally designed for the engine....ever since they put ethanol in the fuel i am fairly certain they didn't adjust the emission standard for older vehicles that were not designed to run on the mix....but i digress.

    if you have stock cats on it, they are probably mostly plugged and need to be removed at the minimum. the good thing about it is that you should be able to just have the shop install a nice single one and it will help in the horsepower area as well as solve your emission issue. glad i live here in Florida
  8. <3 living in MN... no emissions testing FTMFW :banana:
  9. As for the timing. not sure. I know that 89 is still a distributor and 91 was distributorless, not sure what 90's got.

    I know the distributorless ones was all computer controlled, timing wise.
  10. The cat did look pretty old inside an out, as far as the distributor question the 90's had distributors still.