Car is bone stock. Just replaced the cap, rotor, plug wires, plugs, etc. Oil is fresh. Stock exhaust. stock O'2's/cats I'm sure. I've owned this baby since it was 2. 187,000 milses. 5 speed.

Been through the emissions twice now, once before the plugs/wires etc were replaced, the 2nd time after it.

Georgia tests for

HC ppm, it was very low 12 out of 111 allowed.
CO%, also very low .01 out of .61 allowed.

kicker/failure was Nox ppm

1059 out of 773 allowed.

All these numbers were the 25/25 tests. It passed all the 3 categories on the 50/15 tests, although barely on the nox.

I'm a little perplexed on how to fix this thing. It runs PERFECT to me. Better than ever with new plugs/wires. The plugs I took out only had 130,000 miles on them. (oh yeah, great tutorial on here on how to do it). Thanks board.

Any help appreciated. I had a friend I trust tell me as close as it was, to add about a gallon of alcohol to about half a tank of good gas, and he was positive it would pass the test.

PS It has never been close to not passing before, and in the last year, the car has only had about 6,000 miles put on it.

 

Moved to engine forum

 

high nox is mostlikely being caused by your egr system not working properly, have that checked out.

 

^^^^^^^^ very possible. The CEL/ MIL light is not on?
Looking @ the #'s the cars running a bit lean & NOx will
also increase. Possible lazy/slow front oxygen sensor or worse
the cat is dying.
Do few tests first, check the EGR system & the o2.
I'm assuming this is a OBD1 car since your dynoing
the emissions.

 

I concur...

most likely EGR system, second shot o2 sensors (upstream), then possible cats

all three can cause the above...

 

I HEART IL for no emissions on OBD1.

 

you sir are lucky!

 

Thats why I have a full 3" turbo back exhaust with no cats. Hehe.

 

No check engine lights, ever.

Is there any way to check the egr valve?

All/any help appreciated.

 

easiest way I can think (assuming it's vacuum operated as most are) (can you tell I've never done that much work on my SC?)

get the vacuum line that goes to the EGR valve and apply vacuum to it while the engine is running - you should notice a change in the way the engine runs, and it should all but die out... if this happens, then the EGR system is working and no lines inside the EGR are clogged...

 

Hey guys
im having the same issue as well. Maybe you could help me out with a few questions. The car runs great, no pinging, hesitation, smoke in the exhaust and no check engine codes but the same Nox issue

Changed
-spark plugs
-pcv valve
-air filter
-oil change
-94 octane gas
-cleaned EGR vacuum modulator filter

Test Results
HC - 2 / 52 PASS
CO - .03 / .29 PASS
NO - 451 / 385 FAIL


Im thinking of testing the EGR but i have never done this before.
Which tube should I remove to test with a vacuum?
What do i need to get to apply a vacuum to the EGR?

Ive heard that the timing could be too advanced, but my mechanic said that it cant be adjusted on my car, is this right (92 SC400)?
Also Ive heard that i might be running lean, is there a way of checking this? and is this an adjustment i can do myself?

 

A few things I can also add given issues we have with vehicles down here not passing. First of all having the engine running idle for too long (a.k.a. too warmed up) can cause NOX issues. My uncle and my cousins regularly take vehicles to go get inspected and they choose a time of the day when there aren't too many vehicles so they can get in and out and keep NOX low. Too hot of an exhaust and you can get high NOX.

In addition, check the condition/level of your coolant. You don't want the engine too hot and in summer months inevitably is when we have some of the highest levels of NOX in the air.

 

The limits have changes from the last test. Did they key the car
in the computer differently? (wrong year?)
Anyway it's still very lean, HC is fuel & it's low. Try replacing the
oxygen sensor & move on.
To test the EGR apply vacuum directly to the valve. The engine should
studder or stall if the valve is working & the intake passage is open.
Next foot brake the engine to 1500-2000 RPM, should have vacuum
to the EGR valve. If you don't back track till you do have vacuum.
(modulator, VSV, etc.)

 

Got it passed, had a Lexus/Toyota specialist "clean" the EGR valve. Thanks for the advice.