Questionhi there...in BC we have aircare and my 1987 corolla is failing the load test with NOx. its about 4000 ppm (LOTS!) the co is 0%(very low) HC is 240ppm. i've done all the usual tuneup stuff and i wonder if it is the EGR? how do i test it? i have a co/hc analyzer to use and a vacuum source.
Answerput a vac pump to the egr and pump it up.
The motor should stumble badly or stall.
If not the valve isnt working.
The egr is the #1 source of NOX failures.
High Combustion camber temp causes NOX failures.
The EGR allows exhaust into the intake passage to lower the combustion chamber temp.
Other causes are bad O2 sensor, Bad Cat Converter, anything else that causes "lean" condition will raise the combust. temp and raise the NOX reading.
Mike
