Ok so i went to smog my 1989 k5 blazer and i failed my nox was i little too high. the motor is mostly stock just some bolt ons intake manifold , msd coil, new ac declo plugs , new orig GM EGR valve. i swaped out my 160 tstat for a 195 and i also put my stock chip back in . any ideas how to lower my nox with out a new cat thats what they said would help me pass. i did notice my timming was a 3degrees btdc and i think it should be 0 degrees btdc would that raise my combuston temps to high and make the nox high ? Oh and i did the test on 87 octane i think i should have used 91 to burn cooler or maybe a few gallons of e85 to cool things down . any one have any tips thanks .. OH its a Cali smog test

 

Nox is created by way of high combustion temps.There are many ways to lower nox usually at the expense of raising HC's though...What's the read out look like?

 

15 mph hc meas 86 with a max 112 passed that. co% meas0.20 with a max 0.60 passed that nox meas 973 with max 683 failed that .

25mph hc meas 68 with a max 92 passed that . co% meas 0.16 with a max 0.55 passed that . nox meas 827 with a max 585 failed that test

if my cat was bad wouldnt my hc and co be high ?

 

also my truck is lifted with 35 s and 456 gears the inspector was doing the test in over drive and lugging the motor . would it help if he held in first for the first test and then 2nd for the next test ?