Failed smog - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

iamtheyi · 11-22-2011, 04:14 PM

I just failed smog with retarded numbers. My co2 and Nox are okay but my HC is 3-6 ppm over the legal limit. Any suggestions? I was running pulstar iridiums but swapped them out for coppers to see if it would do anything and still failed.

Put fuel injector cleaner in it, seafoamed the car, changed cap and rotor, wires are 7 months old. O2 sensor was also changed this year. Any ideas anyone?

MurkyRiversS13 · 11-22-2011, 08:50 PM

I was going to suggest to check your timing and also you may have a bad cat, but check this link as it has some good suggestions. I just recently went through the same issue but my NO was high/

What causes high HC. What causes high Hydrocarbon - SmogTips.com. Failed HC Emissions. Why did my car fail the emission test for high HC emissions. What is HC. My vehicle failed the emission test for high Hydrocarbons. Why my car produced high HC. Hi

rcdad123 · 11-23-2011, 01:23 AM

i had a customer today that failed smog due to high HC. he failed yesterday also but with much higher out put all across. i performed a top engine service(cleaned the throttle body, intake manifold plenum and runners, intake valves, and piston tops), replaced the spark plugs, replaced the 02 sensor, and did an oil change. after all of this, his measured numbers went down 2/3 of what was measured yesterday. he still failed the HC, but the smog tech believes that it might be excessive oil in the combustion chamber, not fuel, that is causing the high HC. so he recommended Engine Restore to cut down or eliminate excessive oil burning from worn piston oil rings.

11-22-2011, 04:14 PM	#1
iamtheyi Nissanaholic! Join Date: Mar 2008 Location: Brea, CA Age: 30 Posts: 2,252 Trader Rating: (21) Feedback Score: 21 reviews	Failed smog I just failed smog with retarded numbers. My co2 and Nox are okay but my HC is 3-6 ppm over the legal limit. Any suggestions? I was running pulstar iridiums but swapped them out for coppers to see if it would do anything and still failed. Put fuel injector cleaner in it, seafoamed the car, changed cap and rotor, wires are 7 months old. O2 sensor was also changed this year. Any ideas anyone? __________________

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11-22-2011, 08:50 PM	#2
MurkyRiversS13 Zilvia Junkie Join Date: Aug 2011 Location: SoCal / High Desert Posts: 543 Trader Rating: (19) Feedback Score: 19 reviews	I was going to suggest to check your timing and also you may have a bad cat, but check this link as it has some good suggestions. I just recently went through the same issue but my NO was high/ What causes high HC. What causes high Hydrocarbon - SmogTips.com. Failed HC Emissions. Why did my car fail the emission test for high HC emissions. What is HC. My vehicle failed the emission test for high Hydrocarbons. Why my car produced high HC. Hi

11-23-2011, 01:23 AM	#3
rcdad123 Zilvia Addict Join Date: Jul 2011 Location: san diego Posts: 639 Trader Rating: (0) Feedback Score: 0 reviews	i had a customer today that failed smog due to high HC. he failed yesterday also but with much higher out put all across. i performed a top engine service(cleaned the throttle body, intake manifold plenum and runners, intake valves, and piston tops), replaced the spark plugs, replaced the 02 sensor, and did an oil change. after all of this, his measured numbers went down 2/3 of what was measured yesterday. he still failed the HC, but the smog tech believes that it might be excessive oil in the combustion chamber, not fuel, that is causing the high HC. so he recommended Engine Restore to cut down or eliminate excessive oil burning from worn piston oil rings.