Looking for advice after failing CA smog check

[slidahz]

Hi All,

First, just wanted to say thanks for the awesome site/users. I read posts here from time to time and they have always been very helpful.

I recently failed a California smog check and wanted to see what you experts thought about it before I started tinkering around. Everything passed with flying colors except NO at 25mph.

'89 Supra 7M-GE with no mods. Smog passed last year with no problems.

15mph
%CO2: 14.9
%O2: 0.0
HC(ppm): 25 (max 85)
CO(%): 0.08 (max 0.49)
NO(ppm): 74 (max 533)

25mph
%CO2: 14.9
%O2: 0.0
HC(ppm): 7 (max 57)
CO(%): 0.01 (max 0.40)
NO(ppm): 1023 (max 491) :: angry ::

Any advice on how to go about troubleshooting this is appreciated. I was planning to check the EGR and O2 sensors at the very least.

Thanks,
--Robert

 

[jetjock]

O2 sensor is working fine. Forget about it. Check EGR per TSRM.

 

[Maple191]

He has 0% O2 in the exhaust, he needs some O2 to bring down the NOx

 

[mecevans]

Egr.

 

[3p141592654]

He needs to reduce his combustion temps, his 02 is normal. I wish my HCs were that low. Last week I tested at 75ppm, which also happens to be the 'new' limit for 1990 auto. Previously it was 109ppm. I would even take OP's 85ppm, which is for manual trans cars. I'd love to know the logic for these cutoff numbers, since they vary by year too.

 

[jetjock]

He has 0% O2 in the exhaust, he needs some O2 to bring down the NOx

Uh, reduction liberates O2. And the supposed lack of it must be why his HC is so low...

 

[Nick M]

It is carbon monoxide that is used to reduce NOx, but that isn't where he needs to check.

 

[mecevans]

Surprised he passed the function test during the inspection.

 

[slidahz]

Thanks everyone for the replies. I'll check the EGR per TSRM this weekend and see how that goes. Hopefully that's my only problem, but wouldn't bet on it with my luck...

 

[Jimbo]

That's funny, my 89 GE failed the same thing last week.
2 different smog technicians told me the cat wasn't good anymore, and one of them said to check/clean the egr.
How much would a gasket leak on the egr affect this?

 

[Nick M]

How much would a gasket leak on the egr affect this?

Well, the inert gas would have a place to escape. The inert gas going back into the intake dilutes the air charge causing it to run not as hot. Usually, it is plugged with carbon. But you have to lookt at it to see.

 

[3p141592654]

That's funny, my 89 GE failed the same thing last week.
2 different smog technicians told me the cat wasn't good anymore, and one of them said to check/clean the egr.

Post your test numbers, or better yet start your own new thread

 

[te72]

High five to the OP for posting test results before asking aimless questions!

OP, have you had a chance to take a look at things? Always good to have resolution on things like this...

 

[AnubisMK3]

California is really strict, but yes the NO would be the egr. I know a few guys in the Milwaukee area who can mix a batch of fuel additive to mask the problem long enough for emissions lol. I had a Delta 88 DD a few years ago and it worked like a charm.
I'm not sure what California's tolerances are currently, but in Wisconsin they just laughed when i asked about emissions. Apparently foreign cars over 15 years old no longer need emissions. We were about third in the list of strictest emissions states until they shut down 90% of our stations and dedicated the other 10% to specialty vehicles.

 

[jetjock]

What a lot of Californians don't know is the state is far from the strictest both in test method and cut points. In fact most cars in the state go through a much simpler test than the one we're talking about here where NOx isn't even measured and many don't have to do emissions testing at all until the car is sold.

 

[slidahz]

High five to the OP for posting test results before asking aimless questions!

OP, have you had a chance to take a look at things? Always good to have resolution on things like this...

Hi guys, I had a chance to look into the issue further last weekend. I did the EGR vacuum gauge test per TSRM and noticed I was getting vacuum @ 2500 RPM even when the engine was cold (supposed to be no vacuum). After much blood and sweat, I found it was due to improper vacuum hose connections. The BVSV vacuum hose and VSV hose connections to the intake were swapped :cry:.

EGR modulator, EGR valve, and VSV passed the TSRM tests. I replaced the EGR modulator (it was filthy black) and VSV anyway since a friend sent me some spares.

With the above changes, the EGR vacuum gauge test passes... except instead of a 2500RPM threshold it was 2900RPM. Not sure exactly why. Any ideas?

I also cleaned the air filter, intake, throttle body, and ran seafoam through the intake. Boy did I smoke out my neighborhood :biglaugh:. Once I finish off the seafoam I put into the fuel tank I'll take it in for a smog this weekend. Fingers crossed! I'll report back...

 

[slidahz]

Hi guys, back with an update. I failed smog again :: angry ::. But at least overall numbers came down a notch..

Here are the new numbers:
15mph
RPM: 1712
%CO2: 14.8
%O2: 0.0
HC(ppm): 1 (max 85)
CO(%): 0.01 (max 0.49)
NO(ppm): 48 (max 533)

25mph
RPM: 2860
%CO2: 14.8
%O2: 0.0
HC(ppm): 1 (max 57)
CO(%): 0.02 (max 0.40)
NO(ppm): 626 (max 491)

I'm guessing overall numbers came down because of the intake cleaning/seafoam, but i'm still failing the NO at 25mph...

For the TSRM test where you T a vacuum gauge between the EGR modulator and EGR valve, it states I should get ~70mmHg vacuum at 2500RPM, but I don't get that vacuum until ~2900-3000RPM. At 25MPH the smog result states my RPM was at 2860 so I suspect the high NO is because EGR did not kick in just yet. Any ideas why EGR is kicking in late?

 

[jetjock]

Test the modulator, check the modulator's filter, and check for exhaust pressure to the modulator/exhaust leaks.

Seafoam was a bad idea...

 

[suprajztwenty]

this cheat sheet has helped me greatly.

 

[slidahz]

Thanks jetjock and suprajztweny. I'll investigate further this weekend.