I am outputting too much nox, apparently. the, max/610 measured/936 at 15mph and max/498 measured/794. Any ideas about how to tackle this? I have 10 days to fix it or I can't drive the car anymore.

 

Why do have a time table to fix it? I've failed in the past, but never had a time table to fix it. I know people that have taken months to fix it.

 

I didn't think they would send me my registration sticker if it didn't pass.

 

Do what I did, replace the cats and make sure the timing is set at 6 degrees.

 

The guy I take it to checks timing.

 

High nox means you're running too lean. Combustion temps are too high. Could be bad O2 sensor, plugged EGR, vacuum leaks, carboned up pistons, low fuel pressure, retarded ignition timing, timing chain slipped a tooth (highly unlikely though), ect. Go through it and check those things.

Could also be a plugged convertor. Is it original? How many miles on it?

You can check it by looking at the exhaust maniofolds while the car is idling. They usually get real hot (sometimes glow red) if the convertor was plugged up.

 

Now we know what failed, come by and I will show you how to fix the NOX. On your TBI.
What were the other #'s

 

Check his ID (TBI)

 

If you drive with expires registration they will give you a fix it ticket $10. Unless it's more than 2 or 3 months late they usually wont's stop you. They could impound it but never heard of anyone's car being impounded for a late registration on the first time being pulled over. You can pay the fees before it expires and smog it latter without paying late penalties.

 

When my 89 failed it turned out to be a malfunctioning EGR. I replaced it and all was good. And this was on an LO3 with almost a quarter million miles on it (sold it at 225,xxx).

 

Welp, here's an update. I did the diagnostic tests as per the service manual, and found that the NAPA egr valve that was on there didn't hold any vacuum. It was a total dud. I replaced it with a delco unit. The one thing that I don't understand is, if the EGR valve didn't work, why didn't it throw a code? It was the constant popping up of a code 32 that prompted me to replace the EGR several years ago.

Anyway, going to retest tomorrow.

Also, Don, here were the numbers.

 

Did a pretest today; with the new egr it's still 160 nox ppm over passing. I'm not sure what I'm going to do now.

 

Bring it down to Don's shop I guess.

 

I think on tbi cars egress is normally open so vacuum closes it not opens it. Test your egr solenoid. Also set timing to zero degrees and spray Carb cleaner in ALL egr passagess.

 

NOx isnt related to the cat, is it? I remember the last time I failed it was because of the cat, but I dont remember if it was NOx or HC that it affects