Quad 4 Closed Loop Question

My car generally runs good. A problem is that sometimes, about a minute after a cold start, it will stumble for a few seconds. Usually I'll be in a parking lot or in the driveway so it is not much of an issue. Last week it
happened after I pulled into traffic.
A scan tool shows that it goes into closed loop about a minute after a cold start (40 deg F.). It cycles back to open loop then closed several times before it stays closed. This happened before the O2 sensor reached .5 volts. I think that this might be a clue to the problem. Once running hot, the O2 sensor will cycle from rich to lean several times a second.
My question is what allows the engine to go into closed loop?
Thanks
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Coolant temp and the temp of the O2 sensor, late model obd11 engines have a heated sensor, no mention your year though.

----== Posted via Pronews.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.pronews.com The #1 Newsgroup Service in the World! >100,000 Newsgroups ---= - Total Privacy via Encryption =---
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
1995 Grand AM. It is not a heated sensor. I think that the coolant temp was not more than 80 deg. F since it had been running less than a minute before going into closed loop. I'll check tomorrow. As mentioned, the O2 voltage had not reached .5 volt so it should not have been hot enough to work yet. This is assuming that open loop is running rich and not lean not allowing it to reach .5 volts.
What should the coolant temperature be?

in
it
O2
News==----
Newsgroups
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Well we could have skipped the heated sensor issue with having known the year, but as it frequently occurs on these groups, no year mentioned, anyway, the o2 sensor generates it own voltages as the sensor heats up and reacts to the amount of 02 in the exh. stream. Open loop is rich, the .5 volts is default for the pcm to operate from,till the sensor heats up and coolant temps come up.

----== Posted via Pronews.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.pronews.com The #1 Newsgroup Service in the World! >100,000 Newsgroups ---= - Total Privacy via Encryption =---
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Any codes showing up? As was mentioned check the coolant sensor. It can be monitored on the OBDII tester.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
No codes.

in
it
O2
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.