Hi All, I took my 93 Corolla in for an inspection last week and it failed the emission test. The NOx levels both for high speed and low speed were high. I then took my car to a shop to get the catalytic converter replaced. However, when I went back to the inspection station to get it re-inspected yesterday, not only it still failed, but the failing levels were even higher than the first inspection. Can someone please tell me what the problem is?
Thanks, Kenny
================ Check the EGR vavle.
================ Check the EGR valve.
What are the other readings for the emissions tests, ie., Hc, CO?
I would check EGR and MAP sensor operation, depending on the results of the test.
High NOx levels are also caused by high combustion temps. Things like high coolant temp, a really lean air/fuel ratio (manifold system leaks), O2 sensor improper operation, EGR system problems (VSV, modulator, hoses), improper timing and spark advance.
Ray, Other readings are passing and they are: HC: 22 CO: 00 CO2: 13.5 O2: 1.3 Dillution: 13.5
By the way, I know the EGR valve looks like a flying sauce thing, but I can not seem to locate it under the hood. Can you please tell me where I can find it (This is a 93 Corolla)?
Thanks, Kenny
This California Smog Check web site lists common causes for emissions failures:
Not all vehicles have an EGR valve. I don't recall if yours does nor not. The EGR valve is generally located near the intake manifold with a pipe leading to the exhaust manifold.
If you have a 49 state version you need to find a California model first. Then it should be easy to find. :-)
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