didnt pass socal smog

[m00njal]

Just failed smog test today... =(

Apparently in the 15mph (first phase I assume) part my NOx emissions were double the limit, and in the second part, passed, but pretty damn close.


Thurznite just recently helped me replace a knock sensor, and currently I have no other codes. My only mod is a y-pipe (warp speed).


The technician said it could be EGR and/or timing related, just off hand. I understand that I need a proper diagnosis, but any ideas as to where I might want to start? I don't even know what EGR stands for.....and know very little about it. All advice is appreciated.


98 SE with 179600 on odo, y-pipe is only mod.

[aussie983]

Stock y-pipe would definitely help a bit, so if you wanna put that back on temporarily since your WS has no precats. O2 sensors might be getting old and less responsive. Change them out just in case and if you got the cash to. Could be semi clogged EGR tube- search this forum, there should be plenty of threads on the EGR and how to clean the tube.

[m00njal]

Ok, I think I'll swap out the ypipe and I have one newer o2 sensor laying around that I'll install. Will be checking EGR guide tube today to see if its clogged.

I researched the EGR system now into a lot of detail from the FSM, and it just bothers me that though I don't mind checking it, almost all the diagnosis pointed out in there starts with a DTC engine code, while I have none.


Should I be looking into other things? air filter? Intake leaks? EVAP system?

[m00njal]

Update: Scans of smog results

[ewuzh]

Your HC and CO numbers look OK. Sounds to me like your EGR (Exhaust Gas Recirculation, functions to reduce NOx emissions) just isn't working or needs to be cleaned. There should be some articles on how to check EGR valve/solenoid operation on the org, I'm pretty sure it's in the Haynes manual. If your HC numbers were a little higher, it would indicate high combustion temps, possible lean condition, which could mean bad O2 sensors.

[ThurzNite]

If u need any parts, lemme kno. I'll post my numbers, if u like them, take my stuff. haha.
Dr J