When do the o2 sensors get activated? is it after 30 seconds or as soon as the car starts? Also would a fouled o2 cause the car to miss like a bad opti or just make the car run rich/lean?

 

i remember a few replys i got to one of my o2 sensor topics, one thing was that the o2s arent actually used until the car goes into closed loop, and as far as i know a bad o2 would only cause the car to run overly rich (to prevent a too lean condition) hope that helps till someone chimes in wihta definate answer

 

I have always heard they don't do anything until the car reaches closed loop also. And it doesn't go into closed loop until the ECT and o2's get a certain reading. I may be wrong, but that is what I have always heard. As far as the bogging, I don't think that o2's would cause that, but I know that a bad ECT/ECT connector or o2's will cause them to run overly rich. I had a bad ECT connector on mine, and the car was running so rich it was blowing out black smoke constantly.

 

The PCM can not enter closed loop until three things happen:

1. The O2 sensors reach operating temperature and produce the required voltage signals

2. The coolant temperature reaches a threshold value, variable between about 120-140degF

3. A "timer" times out.... seems to be about 2 minutes or less in warm weather, maybe closer to 3 minutes in cold weather.

When you start a cold engine, the cold O2 sensors can not produce any voltage on their own. A scanner will show about 450mV, which is the bias voltage the PCM is supplying. As the sensors start to warm up, they start to generate a voltage, based on the difference in O2 concentrations inside and outside the sensor. With the AIR system intact, the O2 voltage will drop to 00X mV's during this period. When the PCM sees all three items have been accomplished, it switches to closed loop and turns off the AIR pump, and the resulting fluctuatons in A/F ratio cause the O2 sensor voltage to start to cycle back and forth between 0XX-9XX mV's.

 

What else could cause a miss? I have new plugs and new opti, and it happened during a seafoam so im just ruling out the wires.

 

Looking at your dyno graph, it appears you've had a pretty bad miss for quite a while. Is the car throwing any codes? You need to get the car scanned and watch the O2 readings, cylinder misfires, knock count, etc. and see if you can track it down from there. It's possible it's a plug wire, so don't rule them out yet. Best thing to do is to get the car on a scanner.

 

the dyno was from august when i had old plugs and old opti. After replacing my opti it ran near perfect, but then i seafoamed it and during the seafoam it started missing and has been since (a week or so).