Date:         Tue, 10 Dec 1996 11:22:26 -0800 (PST)
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         "Christopher M. Smith" <csmith@sdsc.edu>
Subject:      Exh Emis Gas Analysis ?


I just had my 82' vanagon in the shop to get my air flow sensor adjusted
(requiring CO measurement). The fuel/air ratio was running rich, which I
attributed in part to a new, unadjusted sensor. They also
did a total gas analysis as a pre-smog check. Priot to the air sensor
adjustment, the HC were about 1000 pre-cat converter and 200 post-cc.
After adjustment, the post-cc increased to 250, while the pre-cc HC's
remained about the same.  Since 250 is borderline smog passable, I thought
I'd take it in just to see if I could pass Cal smog (assumming some
shop-to-shop variance in gas analysis). Well, the certified smog shop
indicated my post-cc HC was 30. All other gas measurements (CO, CO2) were
about the same.

I am at a loss for such a big discrepancy in the HC level. I expected some
deviation between the two shops, but not 8+-fold. Does this indicate that
the shop has a problem with their equipment,  is incompetent ? They did
find some other "potential" problems with the engine (a few I was aware
of) that they wanted to do diagnostics on (for big bucks too!, I
declined!). 

Your impressions would be appreciated.

Chris