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Old 01-31-2010, 05:06 AM   #7 (permalink)
cfg83's Avatar
Join Date: Dec 2007
Location: Southern California
Posts: 5,864

1999 Saturn SW2 - '99 Saturn SW2 Wagon
Team Saturn
90 day: 40.49 mpg (US)
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BamZipPow -

Originally Posted by BamZipPow View Post
Well...found out something interesting today.

After a quick minute warm-up this morning...I made my standard runs in closed loop. After the truck sat fer about an hour, starting coolant temp was at 146°F. Started the truck up and waited fer it to go to closed loop. About 4 minutes later, it finally went to closed loop. Coolant temp had risen to 188°F. Ambient air temp was about 45°F. What gives? My normal coolant temp is about 206°F.

I also noticed that when I coast, it registers as open loop when the injectors cut off. Hmmm...
Arghhhh. Everything I am telling you is how my car works. It looks like your ECU/PCM behaves differently.

Let's look at it from a different POV. As a programmer, I might make the decision to *report* open-loop condition when I turn off the fuel injectors. Why? Because when I turn off the fuel injectors, the 02 sensor is not being used to control the fuel injectors. I am not *in* closed-loop operation.

In my 1999 Saturn SW2, this is what I observe :

1 - Coasting downhill in gear. Engine stays *above* 2500 RPM because of slope of hill.
2 - Scangauge continues to report Closed Loop
3 - Digital AFR shows Lean condition, proving DFCO

In this instance, maybe the programmer said, yes, I know I have turned off the injectors, but I also *know* that the ECU/PCM is still in control, so I will continue to report closed-loop.

Regarding 4 minutes to closed loop, I haven't seen that. I have a mild climate, so it is easier for my car. But 4 minutes? With a warm engine? I *want* to say failing 02 sensor, but I really have no idea.


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