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My 97 Honda Civic HX D16Y5 failed emission (HC) CA smog test. My ASM Emission Test results are HC(PPM) Test 15 mph Max 66 Ave 9 Meas 103 Test 25 mph Max 49 Ave 7 Meas 63.
HC
Test 15 mph Meas 103 (MAX is 66)
Test 25 mph Meas 63 (MAX is 49)

My CO and NO reading are very good.

I've completed a complete tune-up: Spark plugs, wires, cap and rotor, valve adjustment, timing set (w/timing light), oil change, cleaned EGR (not dirty) and clean Plenum cover and ports and opened clogged passages, which were clogged) and also I've changed the gas filter and air filter.

I did the work myself. I love the car.

I drove to the smog station about 3 miles away and had the car check and it failed the emissions part only: HC (PPM)

Should I have run the car in the freeway for about 30 hour/30 miles for CATALYTIC converter to heat up enough so that it would pass smog check? Or also for the car computer to run all test?

Also an hour before I went to the smog station I had reconnected the battery because I had finished the repairs on the car.

You advice is greatly appreciated. Thanks in advance.

Fernando Gamboa

 
Rep Power: 234

Possible causes of high HC:

1. You didn't set the readiness indicators by driving for a while before inspection. Warming up the cat shouldn't affect the test as it should go into closed loop seconds after startup.

2. Blowby caused by a bad PCV.

3. Fuel/air mixture too rich. Bad O2 sensor(s) can throw the fuel trim out of whack. They are now recommending changing the O2 sensors every couple of years now.

4. Not enough compression to burn the fuel/air mixture.

 
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Yes, you're are right, cause is of high HC.
I drove the car for 30 miles to heat up the CAT before taking it to smog station. Result where way better than before but I still failed the HC test. Any advice? Fuel additive?
I have replace the PCV recently.
A compression check was performed and it passed. The reading were 160 from what I was told.

3. Fuel/air mixture too rich. Bad O2 sensor(s) can throw the fuel trim out of whack. They are now recommending changing the O2 sensors every couple of years now.

My reading for HC (PPM) where
Test 15 mph MAX 66 MEAS 75
Test 25 mph MAX 49 MEAS 49

What can I do without replacing the CAT or O2 sensor to get the HC to pass smog?

Greatly appreciate your advice.

Fernando.

 
Rep Power: 234

Put some fuel additive in and run it through that whole tank of gas before getting tested again. I recommend fuel additive every few tanks anyways as the ethanol gunks up the engines in all our cars.

 
Rep Power: 367

my miata i had to drive for more than 100 miles until the computer reset was finally checking everything.