NOx Emissions

by Walter Acker

NOx , comes from the combustion temperature going above 2500 degrees
fahrenheit. The main method to reduce this temperature, is to open the EGR valve to recycle burnt exhaust gas back into the combustion chamber. This lowers the combustion chamber temperature

1. Check to see if the EGR valve is opening- idle speed and quality will
.....drop if opened at idle speed

2. If it passes this test with at least a 100 RPM drop then the system
....is at least working

3. Apply vacuum to the valve with the engine off, and see if the valve
....holds vacuum for at least 30 seconds. If not then the diaphragm is
....leaking and should be replaced

4. With the valve off of the car, apply vacuum, and look for proper
....movement of the "Pindle" valve. While holding the vacuum, blow and suck ....through the valve, to see if there are any restrictions in it.

6. For a short time only, see if you can start the car, and get two things.
.......a) Exhaust noise, because it has a direct passage to the exhaust system
.......b) Suction, because it also has a direct port to the intake system.

7) Compare the difference in the idle speeds,

...........a) with the installed valve closed, and ,
...........b) the valve off of the car.

The reason, is that the internal exhaust passages , can plug up with carbon, and reduce the movement of the exhaust gas .

8) This test, needs to be done with a vacuum gauge. See if the hose
.....actuating system is actually transmitting a signal to the valve. On some
.....cars, the vacuum signal will only work if the car is moving.

So, you'll have to tape the gauge to the windshield, and run the hose into the
engine compartment, to the vacuum source for the EGR valve.