Hey guys... I posted a couple weeks back that I failed CA smog... after that I took it upon myself to find out what was wrong. Now, some said it was the cat, some said the 02 sensor... Which I still would like to change... anyway, I pulled the codes on my runner and got a code 25 (which is Air-Fuel Ratio lean Malfunction). I failed the smog test for running rich. I was thinking that maybe the last time the last owner smogged it the truck failed due to running lean and when they fixed the problem they never cleared the trouble code, so the truck is still trying to compensate...?? I don't know... can I get a little help? Thanks in advance! Here are my test numbers.

...........______HC______ ______CO______ ______NO______
..........Max | GP | Meas| Max | GP | Meas | Max | GP | Meas
15mph 121 | 308 | 270 | .70 | 2.00 | 4.08 | 1006|1788| 0026
25mph 101 | 258 | 184 | .90 | 2.20 | 3.89 | 866 | 1588 | 0150

 

sounds like a bad o2, the computer is thinking that the engine is running lean, so it richens it up until it sees the o2 sensor go rich, but it never does because the o2 is not creating a voltage, try changing the o2, i bet thats it

 

Cool cool... my cat is probably shot then huh? since it's been running rich? Should I change that stuff out and then clear the code right after?

 

change the sensor, and remove the negative battery cable for a few minutes, then drive it for a couple days, and then see if it will go through emissions

 

Cool cool. I also opened the EGR modulator and scraped off the "burnt" looking part of it and put it back in. A toyota mech told me that, that a dirty sponge in the modulator is a common cause of emissions failure.

 

anymore?

 

bump!!

 

Ok... so I replaced my 02 sensor last night and I disconnected the EFI fuse and negative battery connector for about 2 mins. After that I put the stuff back together and let it idle for a little bit. I pulled my diag. code again and it was fine! then I drove around for a little bit and pulled it again... it was fine! This morning after going to a meeting and then driving to work I pulled it and it's still doing good! Does that mean I'm doing good enough to get my smog test tomorrow? (I'll drive around for quite a bit before I go in)... Thanks for any replies!

 

I would be willing to wager a good amount on it.

 

Cool! I'm gonna do it then... it's nice to not have to worry SOOO much about this stuff!