On Thu, 21 Nov 1996, Rocko Flamefart wrote:

> the recent post about the 'German Auto' mechanic testing tune-up CO at the
> tailpipe infuriated me, so here goes...
> 
> when doing a *tune-up*, the CO level must be checked PRE-catalyst.
> [snip]
> 
> when doing *emissions checks*, the CO level should be taken POST-catalyst to
> measure the actual emissions from the tailpipe.
> [snip]
> 
 I know!  I know!  When I saw what he was doing I should have said "Sorry
 Charlie" and left.  But I didn't.

 I guess my reasoning (if any) was, "Well, if anything, it's probably a
 little rich to specifications, but OK for smog, so let it go."  

 Question: Will a mistake in the idle mixture have ramifications when the
 engine is under load?  I'm assuming that at idle the mixture is essentially
 controlled by the mechanical position of the mixture screw, while when the
 car is moving the air flow meter/O2 sensor/etc. combine to get the mixture
 right.

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Tom Young               young@sherlock.SIMS.Berkeley.EDU
Lafayette, CA  94549    '81 Vanagon
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