My 1981 B21F 2242DL California has always been like that. The only conclusion I have is that the O2 sensors don't work right until they get hot enough. Therefore, the sensor sends the wrong mixture signal and the frequency valve makes the mixture too lean to soon. Another possibility is in the 1981 Wiring Diagrams green book, the Lambda system is shown with a temp sensor that my car does not have. Perhaps it was to tell the Lambda control box to stay in default mode until the engine was fully warmed up and could tolerate a leaner mixture. The temp sensor would be the third one down under #4 intake with one green wire. The two above are Cold Start Thermo-Time Switch (blue-yellow and white wires) and CIS Temp Sensor (red and blue wires).