

| Subject: | Exh Emis Gas Analysis ? |
| From: | Christopher M. Smith |
| Date: | Tue, 10 Dec 1996 11:22:26 -0800 (PST) |
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
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