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Forum > Failed Smog Test > Question

1993 Toyota Camry 4 cylinder failed NOx. Why did my Toyota fail NOx?

I just did my smog test, everything passed except for the NOx part, I guess the max is like 480 or what ever but my car was like 1100, double that, they say it might be my egr valve, but I'm not to sure, what do you think, and how much would you think it would cost to get fixed?
Answer:

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. posted by SmogTips Support

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