I've seen that the o2 sensors normally don't start working until the car is efficiently warm, is this true? If so, is it the coolant temp. gauge that controls (via the PCM) the air/fuel ratio until the car is warm enough for the o2 sensor to kick in?


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Yes, its true that the car doesn't go into closed loop until the car warms up, however the O2 sensor is working during that time, just not accurately.

The coolant temp does not control the a/f ratio during warm up, its the warmup enrichment and VE tables that calculate it based on RPM and TPS (or MAP if you have a 97 or a S/C reflash). After it goes into closed loop it uses the O2 correction to "trim" the calculated values from the tables.





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ok, i asked because i'm having this problem where when the car is cold it will surge and lag on acceleration, but once it warms up it runs fine. The car starts and idles around 1500-1000 rpms when completely cold and will work it's way down to 600 rpm at idle when warm and it seems to be running a little on the rich side but there are no CELs on. Any idea what might be the problem there?


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