GoudyMan

My 01 Tacoma with 80k miles failed the emissions test in a CA smog test.

@15 mph

%CO2 14.1
%O2 0.0

HC (PPM)
MAX 50
AVG 4
MEAS 65

CO (%)
MAX .64
AVG 0
MEAS .98

NO (PPM)
MAX 508
AVG 18
MEAS 17

The car passed the 25mph portion... but barely passed the HC.

From reading posts on here I am guessing it is an O2 sensor... but the check engine light is not on. Also, it seemed like most people who had to replace the O2 sensor were passing HC, but not CO... I failed both.

Just wondering if anybody else has any other ideas before I take it to the shop and plug it into a ODBII.

AppleJack

I've heard of this problem many times before. The problem is the same each time, you live in California!!! There is nothing wrong with your truck.

GoudyMan

thats great that you think CA sucks. but it really wasnt much help.

Fo_SheeZy

CA doesn't suck, they are just trying to cut down on vehicle pollution which is destroying our planet. I wish every state was like that.

LuminoZ

o2 sensor... plug it in and check for codes... move to colorado

GoudyMan

wouldnt a bad o2 sensor set off a check engine light?

The MAF sensor and air filter are both pretty dirty... I am gonna clean them up. Could that be it or is it something more... like the O2 sensor and/or cat?

infiltrator

damn, my 95 passed CA emissions with flying colors!

try this, go to arco and pick up some of their low emissions gasoline.
works EVERY time.

ive heard that bigger tires can harm your results, and i have also heard that if you drive on the freeway right before the test, your results are better.

do you have any modifications on your truck?

strykersd

I don't touch O2 sensors until I get a CEL for them.


First sea foam your engine, then give it a tune up, check your EGR system (they can get clogged), spray your MAF sensor with some electrical cleaner, change the oil, and change the air filter. Try finding a 'No pass no pay' place, thats what I always do. And finally if that doesn't work it's probably your cats. All these will help your gas mileage too!

rearviewmirror

If there was nothing wrong with his truck he would have passed emissions.

GoudyMan

kragen just quoted me $540 for a new o2 sensor... haha... what the hell?

GoudyMan

i dont think its the tires...
and the EGR affects NOx, which is not the problem.

bwhyit

From what I remember High HC and High CO is caused by incomplete combustion from a rich condition. The fact that your O2 is zero supports that theory. is Check the MAF to see if it's dirty. It should be fairly obvious if so. If not my bet is an O2. You could have a rich bias O2 that is still switching well and will not cause a CEL. I've seen this many times.

bwhyit

Also like mentioned previously take it out and get it nice and HOT before you get it tested. That way your CAT is at operating the most efficient.

bwhyit

Also change your oil and check your air filter. Old engine oil contians HC and get pulled in through the crackcase vent.

j-man

pull out your maf and clean it with quick dry electric parts cleaner - my 2000 runner didnt pass, then i cleaned the maf, reset the comp, drove for 50 miles, and it passed. Make sure you drive for at least 30-40 miles so the computer can reset itself and get the correct numbers.

kmchby76

We don't have o2 sensors in CA we have the A/F Sensor. I would try running some seafoam the intake.

Anubiscougar

Watch out cleaning the MAF, you may damage it... If you're air filter is filthy, change it. You're running lean.

Explanation Below.

HC's are Hydro Carbons, High HC's indicate misfires.
CO is Carbon Monoxide, the higher, the richer.
NOx is heat of combustion (goes up when the engine runs lean, note excessive exhaust temps can damage your cat(s)).
O2 is Oxygen, the higher, the leaner.
CO2 is Carbon Dioxide, is how they measure if the engine is running at stoich or not. An indication as to rich/lean/good condition.

^^From Toyota's training handbook, FYI.

Don't go replacing your O2 sensor just yet. Try the air filter. You're not getting enough air, you said it's filthy... that'll do alot, also do what the other guys said, a good ole oil change, i've heard it makes a difference... i wouldn't know though, i live in FL and don't give a flying rat's butt about emissions... but i do have to know it to work on cars and know how they work/run. We just don't test for emissions...

Don't automatically think that cuz you have high HC"s(misfires), that you have to do a tune up(and you probably aren't even feeling it misfire). It may help, but just in accordance to what i see with the 5 gas, you're just running a bit rich. Which does explain why your NOx is way down... the richer, the cooler. The leaner, the hotter. Also explains your O2 levels

If you know someone with a scanner, get the A/F readings as well as O/2 readings(not sure if it's a v6 or 4, get all the readings). The reading of the MAF as well.. that'll give a much better description as to what's going on. (after the vehicle is warm that is). I'd hate to see you spend cash on a sensor that won't do jack for you when all you need to do is an induction clean, air filter, or some other simple thing.

AppleJack

Easy cougar!! I was just joking with you. I'm sorry my comment wasn't helpful. I was just feeling a little sarcastic.
I meant no harm. 1000 apologies!!

MTL_4runner

X2

Pretty much on target except the front's an A/F (air/fuel) sensor not an O2 sensor on an 01 Tacoma. Also use brake cleaner for the MAF, electrical cleaner doesn't do half as good of a job. Be sure to pull the neg batt terminal and drive for at least 30 miles on the highway before having it retested.

bwhyit

Regardless if you have O2 or AF the basic fuction is the same. And it's not just in CA. If your CA Taco has an AF then all have an AF for that year/model/engine.