temp sensors and closed loop

[IanSzgatti]

From what I understand, the PCM doesn't really care what thermostat opening temp is for closed loop mode, coolant temp requirements are very low, and so the PCM relys on exhuast gas temp, and the time the car has been running to enter closed loop mode.

My engines (not a 60 degree) thermostat is likely stuck open, so the engine has a hard time reaching an ideal operating temp, especially now that here in Canada the temps are around 0 degrees celcius at night. That wind chill keeps my in dash (and properly operating) temp reading at just above 40 degrees celcius, or 115 degrees fahrenheit.
In the MYTHS section of this site, the previous information about closed loop mode was posted, but I suspect the author was refering to cars with temp sensing 02s? Is there such a thing?
My engine, a 3300 from 1991 has a single wire 02 sensor. Unless I am missing something about 02 sesors, I thought my type of sensor merely reated to the amount of oxygen in the exhaust stream, and not EGTs.
If I am correct, I'd like to know what steps the PCM would then use to determine when to go into closed loop mode. I decided to post here because I have a feeling there are some very big automotive brains lurking around here that I would be lucky to tap. Thanks in advance!

[prophiseer]

closed loop parameters are different for OBDI and OBDII applications, and are also different between different vehicle makes, models and manufacturers.

In general, though, closed loop doesn't go into effect until the car has been driven x number of miles with the majority at speeds greater than x mph; the coolant has reached x* in tempurature for x amount of time; if equiped with a post-cat O2, the sensor must be supplying feedback to the PCM; tranny has reached x* in tempurature; and a ton other requirements I can't quite remember right off the top of my head.

Like I said, depends on the car. The biggest difference, though, is in whether or not you have an OBDI or OBDII system. I can tell you, though, if your PCM only ever sees 115F once the motor is warm, it will never go into closed loop.

[IanSzgatti]

This OBD 1 system has one 02 sensor before the cat. It would appear that rather than obsessing over the details, I should simply install my new thermostat. I just figured there would be a common protocol for most Gm cars, whether the engine was a 2.8, 3.1, 3.3, 3.8 etc, all within 1991 year, that defined within its programming what to do when primary data source 1 fails. (like, move to source two for reference).
My engine has a MAF sensor for example, and is the primary for determining air fuel ratio. However, I suspect this sensor does not come into play until the engine is in closed loop. I find the operation of each electronic component easy to understand, but I am still learning how, when, and why they interact with eachother.

[sharkey]

the engine will go into closed loop once you hit a certain coolant temp after running for a certain amount of time.

your ecm is always using all the sensors to determine its outputs. the difference between open and closed loop is in open loop, you ecm is taking the sensors data and using the programmed tables to determine its outputs (injectors, timing, iac, ect), were in closed loop your ecm reads off the o2 sensor to determine if the motor is rich or lean, and makes corrections based on that info, rather than what its programmed.

[IanSzgatti]

thanks

[sprucegagt]

Also the O2 does not measure temperature. The extra wires for O2 sensors, in OBDII vehicles, are for the heater mounted inside the sensor. This heater warms up the O2 sensor to allow closed loop operation quicker than with an 1 wire O2 sensor.