Could Black Bear Tune = failed emissions test??

[TheFuzz]

Could Black Bear Tune = failed emissions test?? **UPDATE: Passed Emissions**

Sorry for the delayed update, but as of 01/11/11, it passed emissions. Check the last page for details.

Hey guys. I just sold my Yukon, and the new owner is saying that it just failed emissions today. By law, I am required to fix it or buy the truck back...which sucks. Colorado just started testing for Nitrous Oxide (NOX) emissions this year. The maximum allowable NOX reading is 2.0, and it's showing 2.27, just barely a failure.

The truck has NEVER failed a test before now. The exhaust is entirely stock.

It has a Black Bear 91 octane tune, and I'm at altitude in Denver. Could the timing changes for the tune have something to do with the increased NOX readings? Any help is GREATLY appreciated. Gotta get this figured out quick.

 

[swtz71]

so you changed the timing ? and now it runs rich? if so that will effect the emissions

 

[TheFuzz]

Well it's a 91 octane tune. I don't know what Justin's secret is, but I would imagine that changing the timing would probably be necessary to make the truck run on 91 octane. It's not necessarily running rich, it's just been recalibrated to run on 91.

The new owner put 85 octane in it against my advice, and the CEL came on due to the knock sensors getting angry. He has since put 91 octane in it and had the code cleared; it hasn't come back on to my knowledge.

It has a AEM Brute Force intake, new MAF sensor as of last year, new spark plugs/wires last year. All regular maintenance. Again, the exhaust is bone stock.

I forgot that Justin has a vendor's forum on TYF, maybe I'll post this over there and see if he or Jenna can get back to me directly.

 

[bowtiefreak]

curious to hear how this goes.

 

[swtz71]

Yea let us know. I don't know why they ran an emissions test when you have an OBD-II port. They should have just hooked it up to the computer. anyway I hope this pans out for ya..

 

[sumo]

maybe swapping back a oe pcm would work and swap the tuned one after passes emissions?

 

[TheFuzz]

Yea let us know. I don't know why they ran an emissions test when you have an OBD-II port. They should have just hooked it up to the computer. anyway I hope this pans out for ya..

Any car thats (I believe) 6 years or older has to have a yearly emissions test in CO. Doesn't matter if it's OBDII or not. They do an OBDII scan (on cars equipped with it) and rolling dyno test at various RPM loads.

maybe swapping back a oe pcm would work and swap the tuned one after passes emissions?

Thought about that option, but we only have 10 days to get it fixed if we want a freebie retest, so I don't really have time to get ahold of Justin, mail him a check, have him mail me a stock PCM and cable, and get it installed and get the security re-learn done in such a short time frame. Besides, the waiting list for scan cables when I did my tune was about a mile long...it took me 3 months of waiting to get one.

Jenna seems to think that it's the cats starting to go bad. I guess that makes sense, as they are the factory originals and are 10 years old...but EVERYTHING else passed just fine besides that slightly high NOX reading, and I haven't gotten any other CELs with this truck. Ever. Period. None.

So WTF? What gives, and what am I missing here? Vacuum leak? Dirty MAF? Clogged EGR valve heating things up too much? Bad thermostat? Somthing simple has got to be throwing this truck out of whack, and I'd really like to figure it out before I go cutting the $800 cats out without knowing for sure they are bad - they may still be perfectly good. I'm not a big believer in "replace stuff one thing at a time until you solve the problem" type of solutions, you know? I'm at a little bit of a loss.

I'm going to have the new owner come over on Friday, and I'm going to clean the MAF and see if I can locate and remove the EGR valve and clean it, too.

High NOX readings are usually caused by too high of a combustion temp, so I'm focusing on things that create unnecessary heat. Any other suggestions are more than welcome.

I'll keep everyone posted, stay tuned.

 

[sumo]

try seafoaming it or Bg induction service. Heavy carbon build up can absorb Fuel making the mixture lean out some. Maybe it will be enough to make it pass. Plus its fun to blast cars down the road and watch peoples reactions as you leave a Big cloud of white smoke behind/

 

[Physh1]

I just smogged my Tahoe here in CA with a 91 BlackBear tune...passed just fine. Well within limits. I'd say cats could be heading south, too high comb temp (clogged fuel filter?), maybe seafoam it...

 

[puckhead]

Damn man, sorry to hear this. Wish I could help out. Hope you get it resolved quick