[s-cars] Smog Check - high HC Level?

[MLP]

Have you checked to see if your MFTS (multi-function temperature switch)
&/or thermostat are functioning correctly.  From C Cohen's recent series of
postings w/ regard to his S2 (below), and other prior threads on the list,
it sounds to me like engine emissions are closely tied to, and greatly
affected by running the correct temperatures.

The adjustments have notable effects on gas mileage too ~ I believe some
listers have reported changes in the order of 3 to 4+ mpg, just by getting
the engine to operate at correct temperature levels!   Sounds like if you
were idling long enough, maybe things finally got warm enough to get you in
range.  What kind of gas mileage are you running?

mlp

-----Original Message-----
From: Joe Petersack

My 1993 S4 with 107K miles almost failed smog check. HC measured 84 PPM, max
allowable in CA is 100 and average is 17 under idle test.  tech had to run
test twice to get it to pass.  One thing different this time was the car was
idling for almost 30 minutes while they were doing other things before they
actually ran the test.  Is this to be expected? Or should I start thinking
about a new car converter?  O2 sensor was replaced at 80K. Joe


-----Original Message-----
From: ccohen5 [mailto:ccohen5 at compuserve.com]
Sent: Monday, April 14, 2003 5:44 AM
To: qlist; urq at audifans.com; Audi S Car List;
Audi20V_Kruemmer at yahoogroups.com
Cc: Frederic L'Huillier; Joern
Subject: [Audi20V_Kruemmer] SQ problem ... solved


It was the temp sensor at the back of the head!  Many thanks to all for some
good advice.

The old one was functioning but the tech could not tell if it was working
within spec.  However some advice from Joern regarding its similarity to the
90/91 200, allowed me to extract some data from a Audi Training Manual for
this engine which had the Ohm/temp spec for this sensor.  AUDIJIM found the
sensor (a Baru equivalent of the Bosch OEM) item as well as the
multifunction/fan sensor jic.

The tech at Currys (VA) had tested the leakdown, fuel system and vacuum
which all cam out ok.  He found after replacing the sensor that he still had
to tweak the MAF.  now I do not know if he had played with this before he
isolated the problem to the temp sensor and had to correct it.  By way of
information, the first emission test run showed the idle at 250 ppm HC which
was over the 200 ppm limit.  Just a half turn clockwise on the MAF adj.
screw brought that down to the high 180s.  This was sufficient to pass the
idle and 2500 rpm tests.  The cat is still not hot enough, but I am hoping
that the next track visit will cure that.

Idle and smoothness throughout the rev range are detectably better.  Boost
may be a little down from its 1.7 BAR spec with the leaner mixture and
probably some Winter Gas.  So before I tweak it richer I am going to wait a
few months.

Colin