Failed smog test

[G_Raw]

Just passed smog, barely though. Read at 478 with the highest value allowed being 508. This was at the 15mph reading. Honestly they always tell me to change my cat when it gets this close. I agree with others here. Change oil, clean MAF and EGR. Run that thing long and hard to heat up well and you should pass. I normally hit a smog spot in the Oakland where I live after driving home from a day trip in Tahoe. This week was the first time I hadn't slogged after a long drive ( 40 minutes of running around doing domestic errands). I suspect if I did an hour or so of freeway speeds it would pass easy.

 

[mkzg]

So I finally passed.

Here is what I did

Seafoam The intake
Seafoam through gas tank
Drove 300 miles
Tested and failed - numbers actually got worse

Replaced Cat
Numbers immensely improved across the board - still failed due to high nox only

Replaced front o2 sensor
Passed with good numbers

So...in the end it required a seafoam treatment, cat and o2 sensor


Sent from my iPhone using Tapatalk

 

[wiricus]

I was in same situation
'97 240k miles, runs great. Failed NOx @15mph (@648, max is 515)
I tried:
-Cleaning MAF
-Cleaning throttle body manually w/ cleaner and shop towel (had a little residue)
-Replacing *Front/upstream** O2 sensor (see note below)

Tested again, failed NOx @15mph (@599). Improved 7% or so but still not passing.
Then I tried:
-Replacing *rear* O2 sensor. Realized that I had originally put the upstream o2 sensor in the downstream position. Corrected positioning (though they seem the same - Bosch Exact Fit for both) ultimately replacing both O2 sensors.
-Used SeaFoam cleaner shot into the trottle body/intake (~10 minute spray). I used this recently, maybe 10k miles ago, never got crazy smoke out the tailpipe and didnt this time either.

Tested again, PASS! NOx @15mph (@161!) Great improvements to all other numbers.

I sorta wish I would have done Either the Seafoam or the O2 sensors so I really knew what was the culprit, but I am guessing the Front O2 sensor.

Anyhow, that was my process to success.
And also, fu*%k those nuts on the O2 sensors! none of my wrenches would fit, had to use vice grips, such a pain. But it done now!

 

[mpalma]

I know a place in garden grove that will pass you for $175. May be a cheaper solution until you can get the problem fixed.
My 97 was 1 level away from failing. (I failed because of tape on a vacuum hose) I took it back the second time and I ran some of the lucus oil cleaner thats suppose to lower emissions and it didnt do a damn thing.

I know this is an old post, but I’m hoping to get the contact info for the Garden Grove mechanic. Thx!

 

[Hungryhawk]

Have you wiped the inside of exhaust pipe to see if it is clean or leaving deposits-a good overview of engine combustion efficiency.

O2 sensors can be tested for ohms with a multimeter to evaluate their condition.

I would service O2 sensors that control fuel first!