hey guys, just trying to figure out what's going on with my car
its a GSR motor with about 40,000 mi
i've changed the CAT, plugs, and oil

first run at 22 BTDC
%CO2 %O2 HC CO NO
@15mph 13.8 0.2 190 0.36 377
@25mph 13.8 0.2 122 0.21 99
I failed HC with the max being 90 and 45 respectively. CO and NO @ 15mph were slightly high as well

second run at 18 BTDC
%CO2 %O2 HC CO NO
@15mph 14.4 0.5 60 0.04 3365
@25mph 14.8 0.2 29 0.12 1751
After adjusting timing, everything else falls in spec but NO numbers run sky high.
Any ideas? I appreciate any help. Thanks!

 

check your egr. insufficient egr flow, and overadvanced timing can cause high oxides of nitrogen.

if no luck still, then you may also have carbon deposits in the combustion chamber. try seafoam if you aren't scared of it (some are, i've used it on 3 cars and never had an issue).