Mustang 5 Oh

I got a 89' 5.0 that failed emissions due to the "Knox" reading. The limit here in Ontario Canada is 757, and my car's reading was 1167. Anyone know what may be the cause of this, please let me know!

- Thanks!

mjr46

check egr, run codes and make sure no egr codes come up, if that is functional, it could be a result of carbon build up in cumbustion chamber = seafoam it, and make sure the cars cooling system is up to par, and car is not running hot

AdderMk2

make sure your timing isnt advanced (more than stock) either

50Stocker

i failed NOX a few years ago with me, just some stupid little things that worked for me...

fresh oil and filter, new air filter, new fuel filter, crc on the mass air sensor (this was the culprit) as it was a little clogged and the dude at the DMV kept banging shifts cause the car was a little fickle at the time. spent like $50 bucks and cruised through, good luck...

HAUS

My limit of N0x in my state is 3600 and I failed with 6970

I only did a few things for that number to come down way below the limit since I didnt throw any codes

Ran premium fuel, Made sure the car was fully warmed with the cats HOT and pulled the Spout so the timing didnt advance.

flew through that time

Riceinator

As mentioned above, ensure that your egr system is there and functional. Also, if you have your timing advanced, put it back to stock and pull the spout connector.
Where in Ontario are you?