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Failed CA Smog, High NOX '89 240

I'm still thinking that you have excess O2 most, or all, of the time, which prevents the cat from cleaning up the NOx even though it's essentially a brand new cat. From the link on the bottom of the page on PCH's smogstats.com link:
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I'd smoke test the induction system for leaks. Injector seals, intake gasket, IAC hoses, intake duct. Pre O2 exhaust leaks throw the mixture off too.
 
Phil.... retard ignition timing five degrees.
NOx happens with high combustion temperatures.
Lean mixture with advanced timing makes for high NOx.
High static compression ratio does too... though this is baked into the cake that is your engine that passed previously.
Be sure that EGR is operational. Added exhaust is inert and takes up space in the chamber for lower in cylinder temperatures.
Be very sure the cat is up to temperature before taking the test.
 
Seems like fixing the vacuum leaks, swap the maf out off the 90 and get the cat nice and warm before the test would get you in the green.

If he's swapping around the cat the same way I do the O2 sensor stays with the exhaust and it just passed, I'd call that known good. Still worth watching the output to see if it's just running super lean.
 
I had high N0X with a great running 740T. Turned out to be sucking in air before the cat. Used a shop vac hooked up backwards to the tailpipe to pressurize the system, found looks between turbo and downpipe as well as the manifold
 
hey thanks guys these are all great ideas... I drove the car to work today and it's got an exhaust rattle that sounds like just about where I was working on things... hmmm perhaps I was in too much of a hurry to get out of the wet gutter when screwing around on it
 
I have a known working maf and a similar magnaflow cat I just used to pass smog. If you wanted to try and swap them in I’m over in Long Beach and usually available on weekends. I also have a easy button if needed
 
Text, call, PM me if you need spare parts. I know you have a parts shed, but I have a couple 740's sitting in the back lot at work with known good MAFs.
 
Update... ok so dug into it today and

Air box flapper was stuck on the hot side (although I have a test only pre-heat pipe with a paint can cap blocking the pipe at the box)
Assorted small vacuum leaks on crappy 86-89 cruise control which I removed
Small hole in intake accordion
EGR pipe at intake manifold baked shut with carbon
EGR valve vacuum nipple ripped off
flame trap is gross
intake manifold is filthy
throttle body is filthy

I cleaned and fixed all this junk and will check out the injectors, plugs and other junk tomorrow unless its raining all crazy again.

Oh also the spark plug wire for #1 was full of corrosion powder and barely hanging on

all this and the thing still drives just like it always has
 
Nice work! Assuming that when you do an EGR activation now, you're getting a noticeable idle drop/ idle quality deterioration (if not, you need to check further down, EGR valve blockage or failure / pipe for blockage). I think that, with all that you checked, found, and repaired, and given the results of your failed test, you should probably be good for a big smiley face on your next test! Note, you can sometimes stack up washers under the base of the pre heat t/stat, to push it further out, and provide more tension on that hot air flap to close it. A fresh oil change never hurts, and could be helpful if you have any fuel in oil saturation issues. Good luck on your test!
 
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I took the EGR valve out of the car and cleaned it out with some gas. It works fine now. The flame trap and it's hoses were oil soaked and gooey
 
The last few EGR valves I have pulled had passages that were almost completely clogged with rust and carbon.
 
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