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Forum > Failed Smog Test > Question

1987 Toyota Camry LE passes HC at 25mph test, but fails during 15 mph, why?

My Toyota Camry passes CO and NO emmissions. Car runs well. Has 218,000 miles. Regular maintenance. Why does car pass at 25 mph and fail at 15 mph. It measured 63 ppm HC during 25mph, and failed HC at 15mph measuring 97 with max at 83.
Answer:

It's true your Toyota passed the smog test at 25mph, however the HC (hydrocarbons) it produced at both 15mph and 25mph are both very high; indicating there is in fact an emissions related problem. Now to answer your question of why it passed the 25mph and not the 15mph, it's simple. The dynamometer puts 50% load on your cars engine during the 15mph portion and only 25% load during the 25mph part. The added strain on the engine during the 15mph portion of the smog inspection will bring out the emissions faults of any vehicle; and so is its purpose. As far as why your Camry produced high HC... The faults may be many, and will depend on what the rest of the emissions numbers looked like. The main reason vehicles fail high HC is defective ignition system. You must ensure your engine's ignition system is functioning properly, by inspecting all the sparkplugs and their wires. The best recommendation I can give is to have your Toyota inspected by a smog check repair station. They will be able to tell you exactly what's causing your Toyota to fail for high HC without you spending money on unnecessary repairs. posted by SmogTips Support

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