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
