Failed smog. :(

[kdog01]

Help. My 240sx just failed smog test.

I drive 1989 240sx. All stock except air filter.

I use Chevron 91 Octain gas with a bottle of injector cleaner every tank.

The hose in blue circle is not connected because my air filter is aftermarket.

What is my problem? How can pass the test? please help me.

ps. This picture is from internet. Not my car.

[kdog01]

I did some research, NO mean high combustion chamber temperature? How can i lower it?

[cd1921]

clean the EGR system, check the hoses..

[hazw8st]

Double check your O2 sensor and EGR, your car is stock, you should have this problem....

[BimmerTech]

NO or NOx is Oxides of Nitrogen. It is caused by high combustion chamber temps. Change the oil/make sure you have the right amount of oil. Check the cooling system. Running to lean can cause that too, since the fuel also cools cumbustion chambers. Check those things.~BimmerTech~

[180fan]

try running some seafoam and clean out the EGR. Replace the vac hose that runs from the bpt to the egr.

[hazw8st]

try running some seafoam and clean out the EGR. Replace the vac hose that runs from the bpt to the egr.

x2

[Red coupe]

EGR should be closed at idle though, I would think that if it was stuck closed it wouldn't show durring the test at idle...and If it were open it wouldn't make things run hotter to form NOx anyways...

Could the unhooked PAIR system be hurting the preformance of the cat when it comes to cleaning up the NOx?

I would go with Bimmer tech and check the cooling system, as well as checking for possible vacume leaks....

[180fan]

High NOx = EGR function problem. Usual suspects the vac hose from the bpt to the egr. Try pushing up on the saucer section of the EGR and see if it stumbles (nearly dies) if so, your egr is still functional, just needs some vac signal to operate.

[andres1708]

Check your egr vacumn source ie the egr solenoid see if its working also may be a weak catalytic converter on your exhaust system....gl

[hazw8st]

Check your egr vacumn source ie the egr solenoid see if its working also may be a weak catalytic converter on your exhaust system....gl