Toyota Repair: idle emissions 85 22R? w/EFI, incomplete combustion, internal combustion

Question
Has 379,000 miles and runs good. Hate to think of parting with it, but it failed for HC idle only. Rest were OK. Limit: 220 ppm; this one: 324 ppm. What to try before retest? Washington state.
Thanks!

Answer
Hi HC readings are almost always caused by an engine misfire, it's caused by incomplete combustion, gasoline consists mostly of hydrocarbons(HC) and if the amount coming out of the tailpipe is excessive it means that some of the fuel is not used in the combustion process, this could be caused by a simple thing like a bad spark plug or an intake air leak to something more serious like a leaking valve, since the high reading is at idle only I would suspect that there may be a valve problem and I would recommend having the engine compression tested and checked for a possible internal combustion leak, possibly a headgasket leak.