Hey gang. The 1992 SC 400 with 242k on the odometer is having trouble passing emissions. I am hoping I can find some help. I searched and saw something about Cats possibly being the issue or maybe sparkplugs.


Any help is appreciated, here are my readings. The / separates the two times they tried.

HC-ppm Reading 263/266 25/25 Test Allowable 108/112 Result Fail
CO-% Reading 0.80/.73 25/25 Test Allowable .60/.62 Result Fail
NO-ppm Reading 1326/1424 25/25 Test Allowable 0751/0829 Result Fail
RPM Reading 1517/1445 25/25 Test Allowable 0-2500 Result Pass
CO+C02% Reading 8.6/8.1 25/25 Test Allowable 6.0 min Result Pass

 

its most likely the cat. did you replace them at all at any point in time? factory cats can go for that long no problem but it may be it. do you have any check engine light on or any codes popping up. the only things that relate to emissions that can cause you to fail...from the top of my head are the egr system, cats, charcoal canister.

good luck with the fix

 

I am in the same boat. At the time I wasn't aware there were 3 cats on the car, and that all 3 were missing on mine. I paid to have a new cat installed and it didn't help one bit. Would adding the upper 2 cats help at all even if the 1 cat had no impact on the readings?

 

was your car fully warmed up when you took it?

 

I'd also say cat, given that I see the NO being so high. We get issues with even new cars down here not passing due to bad gas affecting HC counts, but I only see NO that high when there is a cat problem.

 

Baconator!!!

Emissions....engine...Engine Section.



Moved.

O2 sensors and cats look like the problem with that readout

 

Yes, it was warmed up.

Thank you everyone. So new cats and O2.

What about sparkplugs?

 

With the spark plus, I actually have done a test of sorts without even realizing it. Probably won't make too much difference, but it depends on the conditions of the plugs.

I had a new Magnaflow cat installed about a year ago (my third cat) and then had the exhaust shop I use hook it up to the gas analysis machine (like an emissions test) and kept those numbers handy.

Then went back to my uncle's and changed out the plugs (the very ones shown below), some Torquemasters. The high sulfur gas used does affect the plugs down here. My uncle has seen deposits on other plugs on vehicles we work on, the large majority using the even higher sulfur regular gas.

A week later I went in for a voluntary emissions testing (long story, but doing this allows you to get some special privileges locally), and my HC count was about 5 lower than the day I was hooked up to the gas analysis machine and the air temperature was much hotter at the emissions testing facility.

In my view, it cannot hurt to do this, as it can only benefit, but it just depends on the current condition of the plugs.

One thing to add, the plug on the left was only 1 year old, under 15K miles of use.