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1992 Toyota Corolla Failed Smog Test After Ignition Timing Fixed

My Toyota Corolla failed the first smog check because the ignition timing was off. I had the ignition timing repaired and then the re-test failed again. This time the ignition timing passed but the emissions part failed (which had passed on the first test). I took it to mechanic who "fixed" the timing issue and both he and the smog technician tell me it may be the catalytic converter. It seems strange that the "emissions" part og the smog test passed the first time around and then failed after the timing issue was fixed. Can it be the catalytic converter and if so, what is the approximate cost to replace?

Answer:

It is very possible that your Toyota Corolla's ignition timing being off (more than likely retarded a few degrees) was helping keep emissions low. Advanced timing will usually increase HC, CO and NO emissions. Retarding the ignition timing lowers these emissions, but fails the function portion of the smog test. There is a possibility that your Toyota Corolla's catalytic converter is defective. A CAT "snap" or "intrusive" test will tell for sure. If the CAT does need replacement you should be looking around $400.00 for parts and labor. A California legal catalytic converter for your Toyota Corolla should run between $250 - $300. The remainder you should expect to pay for labor. Keep in mind this does not include any diagnosis fee to ensure the CAT is causing your Toyota to fail the smog check. A smog repair station will usually charge 2 hours of labor to diagnose a smog check failure for a definitive answer on the failures cause. posted by SmogTips Support

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