DXcivicHB

Ok very short, everything passes with extremely lower numbers except the NOx


Nox reading is 1000ppm , with the limit at 634ppm

The timing is perfect, with no CEL's, and a new cat back exhaust with a magnaflow cat purchased last week.

Any Ideas would greatly be apprecieated, im lost on this.

92extremehatch

i failed with the magnaflow high flow cat aswell i pulled it off and put on the oem cat and i passed with flying colours and my car is turbo charged , with the timing set back, 2.5 inch exhaust and way more fuel being added

sohcnotec

Likely running lean, causing NOx to go up.
I'd look into the o2 sensor.

imported_SirII

how's your hc and co readings? if they are pretty low then you can retard your timing, this will decrease nox but may bump up hc and co. i think stock timing is 16 deg? retard it to like 8 or so then go for retest. Also are you running the engine hot before going? If your other readings are low then run the car cold and that should bring nox down too.

DXcivicHB

I was thinking 02 as well but everything else is really low(almost nothing), its just the NOx im struggling with. Its a stock d15b7 should I retard the ignition?

Does anyone think its the magnaflow cat? automotive warehouse assured me it would pass