Nox Problems with 92 Ford Taurus

[99mallard]

Can someone, anyone please help us understand what would make our vehicle emit high nox output?

The emission test limit is .450 and ours is putting out .825

Please, any help would be appreciated.

[TomV]

I am under the impression that the EGR valve recirculates the exhaust gas specifically for this reason.

[hag]

NOx (oxides of nitrogen) are formed whenever combustion chamber temperature exceeds 2500 degrees F or so. EGR cools CC temp. Yes, I know exhaust is hot, but it's also (mostly) inert, so it has a cooling effect on CC temp, and so reduces NOx emissions, and is easily the most common cause the of Taurus high NOx test failures I've seen. A "running" test of your EEC IV system will tell you if the EGR is working. Code "III" (during run test) means it works, but partial blockage of the exhaust passages my cause insufficient flow to get NOx down, while fooling the EEC system into thinking all's well. The second culprit is overadvanced ignition timing, or faulty computer and/ or sensors that cause timing to be overadvanced. Lean fuel and worn out three way cat are the next two, in order of how often I see them. Good luck!

Hag