My 1994 Mercedes E320, 3.2 L recently failed VA vehicle emission test for the second time. It failed on HC ppm @2500 RPM reading 279 limit 125 and on HC ppm on idle reading 145 limit 125. It passed both CO % 1@ 2500 RPM reading 0.64 limit 1.0 and on idle reading 0.34 limit 1.0 and Dilution % at 2500 RPM 14.72 and idle 14.81. Overall it failed. What could be causing high HC ppm? Suggestions/advice/or pointers?

Thanks!

Pete2

Give it a tune up, new sparkplugs , airfilter, and prerun the engine on highway get the cat hot, I had the same issue with my 94 wagon, the test guy told me to replace plugs , my plugs were obviously worn ,passed after driving on freeway ,got the cat hot and passed smog

Sounds like the mixture is OK. HC could be due to incomplete combustion, check/replace plugs, cables, coils. Or your cat could be due for replacement.

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