I am posting a question for a friend that has a 76 280Z & his car runs too rich after the engine warms up in 10 minutes. Could this be the temperature sending unit not operating or something with the ECU ? Any suggestions? Thanks.

Clean the wire connections to the Thermotime Switch. Located on the thermostat housing. The wire connections are a slip fit on the manifold and sometimes corrode leaving a bad connection or the swtich may be defective. This switch tells the computer that the engine has warmed up and it can cut back the fuel enrichment after start up.