The EGR valve has everything to do with NOx production, and it may be very
true that the EGR valve on your Toyota is defective. Keep in mind there are
a few components within your Toyota's EGR system. You have the EGR
transducer, you have the EGR valve, the vacuum lines which control the EGR
valve and the passages which transfer exhaust from the exhaust manifold
through the EGR valve and into the intake manifold. You need to find out
where the EGR system is defective. Your Toyota may have carbon build-up in
the EGR passages restricting exhaust flow; the EGR valve itself may be
defective (torn EGR diaphragm), the vacuum lines which control the valve may
be brittle and/or broken, or the transducer which also acts as a control
valve which controls the opening and closing of the EGR valve can be
defective as well.
We can not recommend simply changing the EGR valve (cost approximately
$150.00), instead have the entire system diagnosed by an expert smog check
repair mechanic in order to identify the actual fault first; not to mention
the high NOx problem, if not related to the EGR, might be air/fuel mixture
related. Have a smog repair shop diagnose your Toyota's high NOx problem
before changing and smog parts. This will save you time and money... we
promise you.
