1998 dodge neon

.  my car failed smog check today.   the reason is the no     ppm was too high  .   m1    15 mph   rpm 1812    co2    max 14.5  %o2   0.0     hc  ppm max  64 ave 9  meas   7     co%   max  0.55     ave 0.03   meas 0.13    no   ppm     max   4.77     ave 67     meas525      result     fail

i replaced plugs .oil and air filter,oil ,one fuel injector prior to the test. tested spark plug wires   .

the idle seemed too fast. i adjusted to lower speed but it still seemed too high.   i just had the transmission rebuilt . i  put in a used fuel pump. changed temp sensor. checked all vacuum lines,  changed the dash gauges.

i did not change the smog valve .  could this cause failure??    i asked the smog person at the star station what needs repair .  he said it could be anything. tired engine ,catalytic converter or something else.      what is the most likely cause of the failure please?

my care engine always seemed powerful. get up and go. one day a fluid line to my transmission burst.
i had to have the transmission rebuilt. now the car does not respond as quickly when i need to speed up to get on the freeway. also the car has failed to pass a star smog check. the ” no” level was too high at 15 mph
can they be a related problem??

what is the most likely to cause a no too high failure at the star test facility


1 thought on “1998 dodge neon”

  1. Two things may be contributing to your high Nox. Nox is formed when combustion temps are high. Lean running will create high combustion temps, and your motor is running VERY lean (extremely low HC and almost no CO). How many miles are on your O2 sensor? If 90k miles or more, you maybe need to replace it – use a Denso direct-fit. Try sparkplugs.com or get the part # from there and search Amazon for denso and the part number. Also there could be a crack in one of the rubber bends of the air hose that runs from the air meter to the throttle body, which would allow air to bypass the meter, so it would tell the computer that less air is going into the motor than really is. Or, perhaps the air meter VS spec is out of range.

    EDIT: Also, check that your idle rpms are not too low. You may need to clean the throttle body, upper and lower air bypasses, throttle plate, with a good throttle body (not carb) cleaner. Don’t allow the solvent to wick along the throttle plate shaft into the tps or otherwise get on or in the tps; that could kill it.

    It’s usually a lean condition and there could be a number of reasons for it. Maybe a vacuum leak, bad O2 sensor, exhaust leak before the cat, EGR… anything that would make it run lean could cause high NOx.

    The vast majority of NOx problems are EGR related (that is THE purpose of the EGR system).

    If you have any check engine light codes, you should pull the codes and post them.

    Some tricks I have heard but not tried>

    usually an oil change, spark plug change, running half a can of seafoam through your intake, and the other half in your gas tank will help greatly. And after putting sea foam through your intake, it will bog down, and blow white smoke for a while.

    Be sure that you use 1 oz of Seafoam per gallon of gas in your tank, otherwise, you are wasting your time.

    Also check your timing. If you’ve advanced your timing, it will increase your emissions, particularly No2. I always run Seafoam through the brake booster line one or two days before smog. It truly does help.

    I’ve heard of a few folks temporarily running small tires for smog testing to raise their rpm which somehow changes how the test readings….

    also if you dont need 91 octane dont run it. run the cheapest gas you can burn. i typically run 87.

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