There are several causes for High HC, basically unburned gas.
Excessive richness cause by a fault in the injection system. high
fuel pressure, bad temp sensor, bad O2 sensor, a bad plug,  bad
timing, etc.  You test the easy things first .  Timing and plugs,
then you check the others depending on what the plugs tell you.

Steve

>I falied CA smog with high HCs on high rpm test.  Took to a vanagon
>place to repair before I retook test.  They said my timing was way
>off and adjusted it.  I past smog yesterday with flying colors.  My
>high rpm hc lmit was 180 and I had 344.  After the timing fix, it
>was 29.
>
>
>
>
>>From: Steve Blackham <ssblackham@MAIL.BIGZOO.NET>
>>Reply-To: Steve Blackham <ssblackham@MAIL.BIGZOO.NET>
>>To: vanagon@GERRY.VANAGON.COM
>>Subject: Re: HC high at Idle - Any Ideas?
>>Date: Tue, 9 Sep 2003 13:03:23 -0600
>>
>>Phil:
>>
>>A leak in the exhaust system upstream from the O2 sensor will also
>>cause your symptoms.  Check for leaks and bad gaskets.  Put a rag
>>over the tail pipe and listen for leaks.  The exhaust leaks cause the
>>O2 sensor to think its running lean from the air leaks.  It
>>compensates by enriching the system.  The volume at open throttle
>>keeps the air out so the O2 sensor operates normally
>>
>>
>>Steve
>>
>>  "Walker, Phil" <Phil.Walker@BROOKS.COM>Wrote:
>><Subject: HC high at Idle - Any Ideas?
>>
>><Well it is inspection time again, only this time I am having emissions
>><problems.
>>
>>My 2.1 engine has about 30K on it and the rotor/cap/plugs were changed about
>>20K ago (3 years). I went in for the emissions and inspection and got the
>>following feedback...
>>
>>RPM 2550
>>         HC        CO
>>STD  220        1.2%
>>Read 59         .61%
>>         Pass    Pass
>>
>>RPM 895
>>         HC        CO
>>STD  220        1.2%
>>Read 505        .26%
>>         Fail        Pass
>>
>>So I combed the archives and I found a post from Steve Blackham in 2001
>>(Steve happens to live about 5 miles from my house!). He was having the same
>>scenario and he documented (quite thoroughly I might add) how he addressed
>>the problem. Most of the fix stemmed from an adjustment of idle and timing.
>>
>>I emailed Steve to get some more advice and he recommended I check the plugs
>>because he thought I might have a leaky injector. Tonight I checked the
>>plugs (all white - chocolaty). While I was getting to the plug under the air
>>filter I noticed the clamp on the engine side of the AFM was very loose from
>>the fuel line job I did a couple of weeks ago (YEA! - I got that done). I
>>basically never tightened it (good thing I've only driven to the inspection
>>since!). Could this also be contributing to the high HC at IDLE? Maybe the
>>O2 sensor is showing lean from the extra O2 so the computer is squirting
>>more juice?
>>
>>Anyway, I'm going to correct that, but I want to do anything else to make
>>sure I pass for sure when I go back. I don't have a timing light, so I
>>hesitant to jump into the idle and advance. The idle is around 900 and
>>although I told Steve it might be a little rough, I'm really not sure. It
>>has never idled like my old Acura legend, but it doesn't hunt. It just
>>seems....well....you know a little weird, but after all it is a VW!
>>
>>I took a look at the cap and rotor and they look descent, but there was
>>nothing suspicious.
>>
>>Any other advice would be helpful. I'm going to do plugs, cap, rotor, and
>>air filter (it's dusty out here in Utah on those dirt roads!)  just to be
>>sure.
>>
>>Steve, thanks for the email. Your advice was helpful.
>>
>>Phil
>>89 Westy
>
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