1993 ford taurus

"janka" wrote: (1993 Ford Taurus 6 cyl 3.0L GL.)

Here in Ontario my car failed its emissions test due to a high NOx level. I?ve changed the EGR valve. Does anyone have some tips for fixing a NOx problem? Which sensors might need changing/any other probable causes? ________________________________________________

Hi NOx indicates air/fuel mixture too lean. The EGR valve richens the mixture, so the new valve may solve the problem. The most likely other source of excess air is a vacuum leak. Sometimes a defective oxygen sensor will fail to trigger the EGR valve.

Good luck.

Rodan.

Thank God you don't work on cars for a living. Perhaps you could explain how Recirculating a portion of the now-inert Exhaust Gasses could possibly richen the mixture?

I had high NOx (albeit on a 94 Mazda Protoge). Catalytic converter solved it.

DW

janka wrote:

NOX is GENERALY the easiest to fix. Only one thing causes NOX - high temps in the combustion chamber. Several things can contribute to this. High operating temps or lack of EGR are the most common. Extreme lean mixture can contribute to high operating temps. So can a bad rad, bad water pump, bad fan. etc. Almost all engines will produce SOME NOX under normal conditions - some more than others - so a reducing bed catalyst is used to clean up the exhaust. If the reducing bed is dead, high NOX can result. The catalyst CAN still be working for CO/hc reduction (which is an oxidizing catalyst)and yet fail NOX.

If you have high NOX, verify the EGR is working, verify operting temperatures, check for oxygen leaks, and replace the converter if necessary.