Smog test failure

I think you have your answer now. I assumed you replaced the front cat, and was not thinking you had two.

 

replaced the front cat, still failed the 15mph test. Replaced an o2 sensor and everything passed now.

 

Glad to hear it! Those oxygen sensors can be a pain. Did you mention you had replaced/cleaned it at some point? Or was I thinking of another post from someone in another thread.

 

Someone had mentioned if i checked my o2 sensors previously, but i said i wasn't sure of their condition because my cel was off.

 

Yeah, always want to check them for accuracy. The CEL will only come on if the sensors does not show crossovers, or the voltages get too extreme. Smaller errors which will not set a code, but will fail smog tests are not uncommon. Congrats on getting it to pass!!

 

a cheap guess would be clean mass air flow sensor with mass air flow cleaner and cross you r fingers. cheap guess without alot of info,also I hate stuff like this but I have heard there is some stupid fuel additive that brags about passing smog guarantee. usually it seems its 02 sensors or mass air flow sensor.

 

Since the OP passed his emissions inspection 16 months ago, your insightful tips probably will fall on deaf ears.

 

Since we are on the topic, can someone knowledgable on the matter post how to check O2 sensors when they are not lighting a CEL. How can you verfiy if they are functioning properly if they are not crossing the threshold to light the CEL?

 

A good technician with a scan tool can see live data from the o2 sensors and it is based on the sensors reaction speed and min/max voltage output, they get slower over time and cause these problems with out throwing a code.

 

Hi taco lovers, me too. I have a 97 tacoma with 250,000 miles yeah! bought it used a couple of years ago and when I had to smog it then it barely passed he HC emissions at 15mph test. now two yeasrs later it failed the HC at the 15mph and barely passed at the 25mph. everything else seems normal. I have changed plugs, wires, pvc, fuel flter, air filter, oil change, and then retested with a little race fuel and using that CRC stuff, but still failed! tester said the catalytic needs to be replaced? should I try the O2 snsors first? dont know if they have ever been replaced? I can post the last three test sheets if that helps? Thanks for any of your responses in advance....fron just some old dude trying to remedy the issue without paying through the roof! thanks again!

 

Tech is mostly right with it being the cats as in there are 2ea. my 2000 will need them next test as they where showing weakness on the test.
They don't maintain operating temperatures on the 15mph part of the test and fail.

 

thanks SDSam, do you know how to tell if they are maintain temp? do you know how hot they should be running? I only see one cat on my 97? I will check again to see if I missed one somewhere. thanks again!