Lorenfb

"My new to me 87 3.2 just failed the CA smog test with a high NOx reading of over 1000. Everything else was okay"

A gross NOX failure is NOT necessarily a CAT problem! And assuming such is a total waste
of money and is indicative of an incompetent repair shop to state such. Furthermore,
proper evaluation of the NOX level requires a load test as done during a CA emissions,
i.e. a simple probe using a four gas analyzer generally yields little info with regard to NOX
under load.

rusnak

To go from reading exhaust gasses and looking at a cat to concluding that the cat is the problem is probably not good practice. What they have concluded is probably that the cat should be changed because it's not factory.

An old O2 sensor, or a broken sensor wire could easily cause the problem. An aftermarket chip or disconnected brown wire at the dme harness will most definitely cause the car to fail smog. There are so many other things that need to be checked responsibly at this point, including the state of tune.

Lorenfb

"To go from reading exhaust gasses and looking at a cat to concluding that the cat is the problem is probably not good practice."

You're right on!

"What they have concluded is probably that the cat should be changed because it's not factory."

That's a potential rip-out, as most/all visuals are concerned about whether the CAT is present
and not whether it's an original factory replacement as most factory replacements for most
cars are no longer available.

"An old O2 sensor, or a broken sensor wire could easily cause the problem. An aftermarket chip or disconnected brown wire at the dme harness will most definitely cause the car to fail smog. There are so many other things that need to be checked responsibly at this point, including the state of tune."

Again, right on! Too bad this guy is in SoCal, as he should drive to you for further insights, seriously!
Too bad he's potentially being 'taken-down-the-path' of spending big bucks and that others didn't
provide these insights before suggesting where to immediately take the car.

As a good example, one of my vehicles has over 500K miles with the original O2 sensor
and CAT. It failed NOX with a 1800 reading at the 15 MPH test. Cleaned the EGR and
the NOX dropped to 1050 and again failed. Retarded the timing a few degrees and the
NOX dropped to 600 and passed, i.e. limit was 1000. As many would have said, "Oh, it's
time for a new CAT."

Bottom line: A CAT has a lesser effect on NOX than it has on HC and CO.

s329

Update:

So I dropped off the car at callas rennsport in the morning and picked her up in the afternoon. According to Tony, car had a pre-muffler in place of the cats. I'll take a photo of the part later to get your opinions on it. Installed a used Cat with a heat shield and the guys did the smog test for me. NOx numbers went from 1327 a couple days ago to 341 today (at 15mph) CO% went from 0.73 to 0.03. Car definitely smells less now. Bottom line issue fixed and i couldnt be happier with the service and results.

I'm clearly out of my element with the 3.2 cars and I'm still getting used to the G50 gearbox so I appreciated the wealth of information and knowledge on this board. Look forward to a great ownership experience!

rusnak

Absolutely, Loren. That's how I got the Ford F150 to pass. Retard timing a bit, and Bingo.

S329, good job! Go have a beer now!

tone40

Tony

Brett San Diego

You should still have the engine baselined with a full and proper tune, if this wasn't done already during this service episode. You don't want the cat to mask a possible out of optimum tune situation.

Brett

Lorenfb

"You should still have the engine baselined with a full and proper tune, if this wasn't done already during this service episode. You don't want the cat to mask a possible out of optimum tune situation."

That's exactly right! Given that most 3.2s will pass even with a bad CAT.

rusnak

+1 Amen!!!

A badly out of tune or overly rich mixture, old O2 sensor, etc will quickly ruin the "new" cat.