Yeah I read the faq, but I did a tune up, and I still failed with high HC. The max allowed was 90 and my 7 was readin' 158, not too bad I guess but I was just wondering is it the O2 sensors fault? This car was sitting for 2 months after the tune up, with the exception of a new exhaust and starting it a few times to test it, wondering if that caused any problems too?

Thier guide suggests it might be something to do with the carburetor, fuel injection, ignition system, vacuum leak, EGR valve, 02 sensor or cat.

 

anyway I can move this topic to general automotive?

 

It is doubtfully related to the o2 sensor as it is only used when throttle has been steady and rpm are under 3500rpm. My alternator had been bad and I repaced that first, the less load passed me the first year. But later, my cat clogged and so I replaced it and passed with flying colors.

 

I swear by a fresh cat for etesting...Ive never had any issues *yet*

 

I second that motion.

If you have done a tune up and are high on HC's, You just probably need a new cat. I keep a new one in the garage to re-use every year. On and off in less than an hour.