...you guys are making me teary eyed...

 

The ECM's timers are not the same for a hot vs. cold engine.
The timer varies for cold, warm, and hot operation.

Even if the O2 is still hot, the ECM must wait on a timer to go off before it reads the data, and these time durations are different.

If you have a chip reader/writer program you'll see the length of the timers.

 

How soon is "immediately" and what are you using to verify this? I don't have access to my chip software at the moment, but my "hot engine O2 timer" is 30 seconds. The cold one is 300 seconds. I forget what the warm one is at the moment. Somewhere I have the coolant temps that determine which timer is used.

I've watched it numerous times. Even if my car has been running for hours if I turn it off it won't go closed loop for 30 seconds if restarted immediately. Its like clockwork. I've adjusted this timer before and seen the change take place exactly at the time I set it to. Perhaps 84 is a little more different than I suspected?

 

If you have a service manual, head for Driveability and Emissions.

For the Model Year 90-page 6E3-C2-2(L98)

Run Mode

"The system stays in Open Loop until the following conditions are met:

1. The O2 sensor has varying voltage output, showing that it is hot enough to operate properly. (This depends on temperature.)
2. The Coolant Temperature Sensor (CTS) is above a specified temperature about 40C(104F).
3. A specific amount of time has elapsed after starting the engine.
Specific values for the above conditions exist for each different engine, and are stored in the memory calibration. (MEM-CAL)."

(My note:EEPROM in later years)

The GM Fuel Injection Diagnosis manual says the same thing.

I tried to find a reference suggesting some elapsed times but no specific times were mentioned. I suspect all three have to be met. Not sure if these are "AND" gates or what.

Mr Probst in "Corvette Fuel Injection" lists the same criteria but uses different temps and lists a voltage instead of a temperature. This would obviously correlate with a temperature when the O2 sensor is active.

At any rate, time appears to be a factor in switching from open to closed loop.

 

This is coming from someone who doesn't know Bo, so don't freak on me.
From what I have read, I would think that the 02 would have a temperature with a corresponding voltage, and the "timers" are actually delays based on input the ECM receives from the sensor itself.

This is a good thread, how do I save a thread with out subscribing to it?

 

From: http://www.tunercat.com/pdfs/ecm_$32b.pdf

87/88 Corvette

Hot Engine O2 Timer
Warm Engine O2 Timer
Cold Engine O2 TIimer
Min. Coolant Temp for BLM Update (Maybe these 2 are the other trigger?)

Max. Coolant Temp for BLM Update

From: http://www.tunercat.com/pdfs/ecm_$32.pdf

86 Corvette

Hot O2 Timer
Warm O2 Timer
Cold O2 Timer
Min. Coolant Temp for BLM Update
Max. Coolant Temp for BLM Update

From: http://www.tunercat.com/pdfs/ecm_$1f.pdf

85 Corvette

Closed Loop DelayTimer, Cold Engine
Closed Loop DelayTimer, Warm Engine
Closed Loop DelayTimer, Hot Engine
Minimum Closed Loop Integrator Value
Maximum Closed Loop Integrator Value

p.s.

I wish the search was working. About 1 year ago we had a great thread on this that included actual source code from the ECM showing how the timers worked and what temperatures were used for each timer.

 

No prob, here. Again, if I had seen the one post before I wrote, it would have been different.

Different timers based on engine temp, helps explain things. Again, I never disputed the existence of timers, but I think we all agree that no mater how ready everything is for closed loop, it won't happen until the O2 is up to temp and sending usable information. The original question asked the difference between open and closed loop, and the purpose/advantage of a 12v connection.

I haven't timed it to say how quickly closed loop occurred. It seemed immediately, but with fooling with test leads, I can't quantify, "immediately". I use the ECMs "field service mode" to differentiate between open and closed loop.

Although the '84 has an older, slower, ECM, I doubt it is really all that much different in the theory of operation.

My service manual doesn't even have a "6E3" section. My book does say in part:


Especially in light of the first sentence, I interpreted that to mean the the O2 would require 30 seconds to 2 minutes to heat up. But because there IS a minimum of 30 seconds mentioned, and since enlightenment, I see it does hint at the possibility of the existence of an unmentioned timer.

RACE ON!!!

 

Excellent. Looks like the minimum value for certain applications is 30 seconds to 2 minutes. I searched all over the MY90's manual and couldn't find a single range listed. Suspect the values posted in my service manual are "AND" gates and all three minimum cirteria must be met. This is pure speculation on my part.

Just to futher muddy the water, I suspect OBDII may even be faster.

Now then, anybody for going back to carburators? (spelling?)

Hope everyone has a nice weekend.

dlmeyers 90 coupe zf6 speed shocks

 

It HAS to be "AND". We all know the O2 is useless until it is ready.

Screw carbs!

RACE ON!!!

 

Anyone have a link to an old thread for converting over to a heated sensor from a single wire?

 

One of the easiest ways is to utilize a small relay. Tap into the fuel pump relay for the "on" condition and then run a line to a constant 12v source.

 

Thanks, I was thinking a relay would be the ticket

 

Im running a three wire heated 02 sensor - Bosch 13190 ($44 from AutoZone).

Has two white and one black wire.

The black wire goes to the original 02 lead

The white wires are interchangable:

One goes to a good ground and the second one goes to a switched 12 volt source (only energized with the ignition key in the "Run" position.

Hope this helps.

Jake

 

How does this help the overall running of the engine?
What's gained by going into closed loop earlier?

 

I had to move to a heated 02 after installing long tube headers. The headers caused the system to drop out of closed loop at idle when the 02 sensor cooled down below the 600*F temp required for feedback to the ECM.

Jake

 

I get it.

 

That's how this 30 something post thread got started.

RACE ON!!!

 

In the constants table there is 3 closedloop delay timer settings.
Cold-300 sec
Warm-206 sec
Hot-50-sec
Hope this helps this is on a 85

 

Contents table of what?

RACE ON!!!

 

Constants table of ECM code. Like the ones I posted up a few posts.

p.s.

I looked the stock '87 values and they are as follows

Hot Engine O2 Timer: 066 Seconds
Warm Engine O2 Timer: 206 Seconds
Cold Engine O2 Timer: 300 Seconds