Passing Smog


Asked by Apr 28, 2011 at 02:24 PM about the 1993 Nissan Sentra XE

Question type: Maintenance & Repair

My Nissan Sentra 1.6L has 200,000 miles on it it passed smog two years ago with flying colors now the H/Cs are too hight did a tune up? It's at the 15 mph speed that the h/cs are around 150ppm anyone have any suggustions?

2 Answers


Hydrocarbons are fuel, which means you're not burning enough of the gas that's going into the cylinders of your motor. Try the following: Check the ignition timing is within the parameters detailed on the VECI sticker. Replace the distributor cap and rotor, and the spark plugs. Check that you have proper compression in all cylinders. Make sure you do not have any cracks in the intake tubing, or bad vaccuum lines - any unmetered air can cause a lean-mixture misfire that will result in a high hydrocarbon reading. If none of that works, you may need a new catalytic converter. Is the vehicle's check engine light on?

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