Stalling on warm up after new O2 sensor

[whitefox]

After having some really bad surging and other probs, i did some research and eventually put in a new oxygen sensor. When the engine's cold, it starts up just like before, rpm's go up to 1400 for about 30 seconds. After that, instead of rpm's dropping to 1000-1100 they drop to about 400, sputters, rises to around 700, then drops to zero. (This all happens in about 4 seconds) but starts up and runs fine after that. This happens everytime it starts cold and it never used to stall. I've previously installed a new fuel pump/filter, and did a major tune up not too long ago. Anyone have any idea why a new O2 sensor would do this? What's the recommended ft lbs to torque the sensor at?


'88 N/A 2.3