Tips to pass CA smog

[eflat]

I'd like some tips (additives, etc) on what I can do to ensure my car passes it's next California smog check next year, since it seems it barely passed it's last check.

It's a 99 Mazda Protege with 320k miles. It was sitting for about year when I put in a newer engine (with 94k miles) earlier this year. The smog check brought the registration up to date a few months ago. There was one category that to my untrained eye looked like it was pushing the pass limit. Wondering if the newer engine being dropped in less than a month before the test would have a big effect. Any opinions and interpretations of the results are appreciated!

15mph -- RPM = 1874, %CO2 = 15.1, %O2 = 0.1
25mph -- RPM = 1807, %CO2 = 15.1, %O2 = 0.1

15mph -- HC(PPM) = 47 [max = 64, ave = 9]
25mph -- HC(PPM) = 10 [max = 47, ave = 7]

15mph -- CO(%) = 0.22 [max = 0.55, ave = 0.02]
25mph -- CO(%) = 0.19 [max = 0.54, ave = 0.03]

15mph -- NO(PPM) = 459 [max = 477, ave = 57]
25mph -- NO(PPM) = 31 [max = 764, ave = 50]

 

[bdcardinal]

Cat failures are real common on Proteges, mostly the car that bolts directly to the exhaust manifold.

 

[sciphi]

Drop some Amsoil PI in the gas, and give it a thorough tune-up. Plugs, wires, PCV, clean the MAF sensor, maybe replace the front O2 sensor. Plus a fresh oil change a few days before the smog because it's rumored to help for whatever reason.

And go to the smog station after a spirited or long drive to get the engine and catalysts up to operating temperature.

 

[PandaBear]

NOX and HC at low speed is usually lazy O2 sensor.

 

[Stu_Rock]

I second the suggestions for sensor upkeep--especially O2 and MAF. High NOx could be an EGR issue, so check that out. But the NOx went down at high-speed, so the EGR is probably OK. A catalyst with 320 Kmi is also going to be a "usual suspect."

That said, I wouldn't be surprised if this car passes its next smog test. I have an old but low-mileage non-CA Dodge van that has passed smog both times, but with near-failures in different categories each time.

Be sure the car is fully warmed up right before the smog check. Don't warm it up with a lot of heavy-footed driving; the rich exhaust could starve the oxidation reactions (HC & CO) in the cat. But don't lean it out too much either (how you would do that depends on the car), because that could suppress the NOx reduction reaction. Moderation is key.

 

[spasm3]

i used to run the tank down low and then use a lot of alcohol ( like denatured alcohol. About 15- 20 % alcohol to fuel us what i used to use to pass the test. ( north carolina test i don't know about ca.)
Just fill up right afterwards, you dont'want that much alcohol in the gas all the time

 

[eflat]

Wow - many thanks for pitching in here!

Man, the thought of o-sensor issues makes me twitch. I had both need to be replaced not too long out of warranty, with basically no aftermarket available. Insanely priced. A quick search shows I have more reasonable options now.

I'll heed your advice(s) come test time - thanks again.

 

[mopar_monkey]

make sure it is as hot as you can get it right before you have it tested, hit the freeway or drive around for 30 min or so before hand.

 

[PandaBear]

Usually the guy testing it will adjust all kinds of things (location of the tail pipe detector, throttle, waiting for things to warm up, etc. If you go to a place that has free retest, you usually don't fail unless you have something wrong on the car.

 

[tom slick]

Originally Posted By: spasm3
i used to run the tank down low and then use a lot of alcohol ( like denatured alcohol. About 15- 20 % alcohol to fuel us what i used to use to pass the test. ( north carolina test i don't know about ca.)
Just fill up right afterwards, you dont'want that much alcohol in the gas all the time


That works in Calif. also. I've done it myself.