# High hc **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** chevrolet\ **Created:** [January 1, 2011, 11:57pm UTC](https://community.cartalk.com/t/high-hc/59396 "2011-01-01T23:57:01Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![nutcase22](https://avatars.discourse-cdn.com/v4/letter/n/b5ac83/32.png) [@nutcase22](https://community.cartalk.com/u/nutcase22)\ **Post date:** [January 1, 2011, 11:57pm UTC](https://community.cartalk.com/t/high-hc/59396/1 "2011-01-01T23:57:01Z")
hc 517 should be 220 no codes coming up new air cleaner & plugs,can a bad cat do this? ---
**Author:** ![ok4450](https://avatars.discourse-cdn.com/v4/letter/o/e9bcb4/32.png) [@ok4450](https://community.cartalk.com/u/ok4450)\ **Post date:** [January 2, 2011, 1:31am UTC](https://community.cartalk.com/t/high-hc/59396/2 "2011-01-02T01:31:13Z")
It might help if info about the vehicle was provided; mileage, any oil consumption issues, year model, etc. It’s possible a bat cat could be behind this but there are too many other things that could cause it. A bad cat, if it exists, may be symptom of another problem. ---
**Author:** ![edb1961](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/edb1961/32/122_2.png) [@edb1961](https://community.cartalk.com/u/edb1961)\ **Post date:** [January 2, 2011, 1:59am UTC](https://community.cartalk.com/t/high-hc/59396/3 "2011-01-02T01:59:31Z")
It would be easier for all if you replies to your original post instead of starting a new own. As Ok said, year, model, miles is important. My 93 Caprice was 100x over the limit for HC when I took it in for NJ Inspection last summer. Two years before it passed with flying colors. Evidently if an OBD-I car sits too long in the inspection line the Cat will not be hot enough to work properly. Before I took it back for reinspection, the PCV valve and O2 sensor was replaced ($23 total). I drove about 40 miles the day of the reinspection. This time there was no line and the Caprice passed emissions. Ed B. ---
**Author:** ![nutcase22](https://avatars.discourse-cdn.com/v4/letter/n/b5ac83/32.png) [@nutcase22](https://community.cartalk.com/u/nutcase22)\ **Post date:** [January 2, 2011, 2:35am UTC](https://community.cartalk.com/t/high-hc/59396/4 "2011-01-02T02:35:01Z")
OOPS, sorry 95 chevy pu 5.7 2500, 152k no oil burning or loss ---
**Author:** ![nutcase22](https://avatars.discourse-cdn.com/v4/letter/n/b5ac83/32.png) [@nutcase22](https://community.cartalk.com/u/nutcase22)\ **Post date:** [January 2, 2011, 2:37am UTC](https://community.cartalk.com/t/high-hc/59396/5 "2011-01-02T02:37:22Z")
Thanks ---
**Author:** ![edb1961](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/edb1961/32/122_2.png) [@edb1961](https://community.cartalk.com/u/edb1961)\ **Post date:** [January 2, 2011, 6:32am UTC](https://community.cartalk.com/t/high-hc/59396/6 "2011-01-02T06:32:55Z")
95 was OBD-I, so the cat has to be good and hot to work properly. I had to take the Caprice to the State Inspection facility, the local dealer doesn’t even test OBD-I vehicles anymore. Ed B. ---
**Author:** ![Caddyman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/caddyman/32/23_2.png) [@Caddyman](https://community.cartalk.com/u/Caddyman)\ **Post date:** [January 2, 2011, 6:46am UTC](https://community.cartalk.com/t/high-hc/59396/7 "2011-01-02T06:46:50Z")
High HC (hydrocarbon) is misfire, pure and simple…Unburned gasoline vapors going out the exhaust…Timing that is advanced too far can cause high HC readings. A vacuum leak. EGR valve leaking. A burned valve or two… ---
**Author:** ![nutcase22](https://avatars.discourse-cdn.com/v4/letter/n/b5ac83/32.png) [@nutcase22](https://community.cartalk.com/u/nutcase22)\ **Post date:** [January 2, 2011, 4:31pm UTC](https://community.cartalk.com/t/high-hc/59396/8 "2011-01-02T16:31:58Z")
Thanks ,I did find a vac keak at boot for the pcv valve, also, how do you check the cat to see if its good or bad?