It's saying my NO failed??

I've got Hooker 2055's w/ AIR, a 3" Magnaflow Cat, and a Dynomax 3" cat-back.

What gives? Doesn't it mean I have a bad cat if my NO failed?



I've got a 350 showing up later this week, and I just might wait until that's in before running the test again, but I'm not sure it would make any difference seeing how the cat is still new.

 

Could be bad cat. More like an EGR valve that isn't working. NOX is a by product of a hot combustion chamber, the nitrogen in the air used for combustion becomes unstable at higher temps & exhausts as NO, NOX. You need to explore the possible reasons why you are on the border of a "ping", check egr function, if it doesn't work, fix it & you should pass, set base timing to spec, maybe even a little retarded, run higher octane fuel for test, make engine fan come on earlier if possible. There are theories of different things to put in the tank, some work, some don't , some actually hurt emmissions. If I had to pick one additive, methanol. Add 10% methanol to fuel & octane goes up 5 points, methanol has an octane rating of 113. But I would lean towards the mehanical fix first.

 

Thanks for your help.

Well the cat is brand new, like 2 weeks old. And the EGR Valve was put on just prior to me going to Afghanistan, so it's only about 8 months old.

The timing is bumped to 8*, so that might have something to do with it.

My father used put this stuff in his 90 Caprice w/ a 350 TBI w/ 250,000 miles on it, and it passed. It promptly had the compressor crap out after, but that's besides the point.

I also always run atleast 93 octane, because of my advanced timing, but I'll try what you suggest. . . put my timing back to 0* and either add some methanol or some of that "octane booster" stuff.

Thanks again.

Anybody else w/ any ideas why this thing isn't passing?

 

Put the timing back to stock, should run a bit cleaner. Not sure if they do a check on what the timing is set at but here in CA, if it's more than 3* either way from factory they fail the test. Now they can even fail a newer car if there's a trouble code stored in the computer

 

Most of the time when people have EGR valve problems it isn't the valve. Usually its buildup in the passage from the head to the intake.

Also a guy I talk to couldn't get his to pass NOX. It was because his EGR wouldn't open because he had more free flowing exhaust. He got some kind of reverse vacuum one or something that opened sooner and it passed.

I will have him post if I talk to him.

 

As ghetto as it sounds, if the problem is because the exhaust is too freeflowing, why not plug up one the pipes? Of course as a temporary thing just for the emmissions test.
And the EGR would throw a code, would it not?

 

The exh backpressure is true, the egr valve is a "dual pressure" valve, meanining it needs exh pressure to close a diaphram within the valve to allow the vacuum to work. If you have a cat, you probably don't have a problem with this, but it's not out of the question.