No I didn’t put anything in the gas tank.High NOx can be from mix too lean or high combustion temps.
Did you put something in the Gasoline?
Timing too advanced? (you can have it retarded 2* and still pass).
Hey FrickreHad the same problem a few years ago. Here’s my post from back then when I finally passed.
Hi All- I've had quite the education cruising this site for the past two years... thanks to you all. I failed smog (CA) for the first time since owning the rig and figured I'd write down my experience so someone else can learn from it! Thanks to the info on this site, I passed. Here it goes...forum.ih8mud.com
You have low O2 and that might mean you have the same problem I had- no air injecting into the exhaust. Read through that post and DM me if you want to jam on it.
Oddly enough I think I went to the same exact Smog station you did when I first bought my truck!
He actually did Check the timing!The combustion temperature is too hot. Almost every tech never checks the timing on these cars.
If yours won't, retard the timing a few degrees and swap the vacuum hoses going to the vacuum advancers on the distributor.
I am going to triple and quadruple check again.Are you absolutely positively sure that your EGR is working right? I had numbers really similar to that a couple tests ago, when I forgot to take a little BB out of the vac line from the EGR vac modulator to the top of the EGR valve (long story). Low HC, low CO, residual O2 around 1.5, etc. But NOx in the 2300 range. So I tested vacuum on that line and suddenly remembered what was in there. Pulled it out and passed. HC and CO came up a little but not enough to fail.
I know you have checked and checked but this is just my hunch.
Would that be installed after that air injection pipe? Or before?Save your money on the Dyno. Buy a good A/F meter. Weld, or have welded a bung in the downpipe, and save yourself countless hours trying to troubleshoot this crap.
Your numbers are so close, I think just a slight tweaking of the mix and timing would probably do it.