164S Failed CA Smog Check

["Rich Lasner" <rlasner@domain.elided>]

I took my 164S in for its bi-yearly California smog check today. Two
year's back, at the last smog check, the O2 sensor was dead (got the
code from the Motronic unit AFTER I failed) and I narrowly missed being
branded a Gross Polluter. This time, somewhat confident that all was
right, as the O2 sensor was the OEM part, I again failed. The car at
first seemed to be smog-legal over 2500 rpm, but refused to stay stable
for the emissions to pass at idle. I checked the Motronic codes and sure
enough, found the 1-2-1-4 code: Coolant temperature sensor trouble.

I replaced the coolant temperature sensor not more than 8 months ago
after a coolant leak shorted the last one out. The connector wires have
enough slack and the connectors seem fine. I cleaned them with DeOxit
and cleared the code, but it came back in minutes. I didn't loosen the
bolt holding the ground wire near to the thermostat housing to clean
under it to ensure a good contact. The smog test showed the fuel mixture
hunting from OK to very rich. I pulled the idle mixture device off last
month and cleaned it out. It was working fine. I'm looking at replacing
the coolant sensor tomorrow and trying the smog test again. Anyone have
an idea of whether I'm on the right track? Thanks in advance for the
help.

Rich Lasner
92 164S
ARA
AROC
Mill Valley CA

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