High HC on California smog test

HONDA CIVIC

IRISHMUSTANG

MEMBER
7 POSTS
FOLLOW

I have a 1986 Honda Civic DX 4WD manual trans with a carburated 1500cc engine. It has 156,000 miles. The first smog test it failed HC at idle with 179 (120 is max allowed). It passed at 2500 rpm. So I changed the plugs, cap, rotor, air filter and the breather filter. I also pulled the egr valve cleaned off the carbon and vacuum tested it. It holds a vacuum. I checked and corrected the idle speed and timing. I took it in for a retest and the HC are down to 139 at idle, thus it still failed. After telling the tech the work I did he suggested a new catalytic converter. Is this my best bet, or should I try a new O2 sensor first?

Mar 20, 2007 at 1:50 AM

BRUCE HUNT

CAR REPAIR CONTRIBUTOR
3,754 POSTS

I would opt for the O2 first and then see how that comes out. Less money, however, they usually work fine or fail. Whereas, the convertor can be slowly plugging and losing efficiency. Your call & $. You seem to actually have things well in hand. Good job.

Mar 20, 2007 at 9:37 AM

Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.