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Open/closed loop?

 
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slowsol
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2004 Chevrolet Impala
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PostPosted: Fri Dec 23, 2011 11:22 am    Post subject:  Open/closed loop? Reply with quote

The last few weeks I have noticed my scan gauge telling me the car is in open loop under normal driving conditions. I first noticed it when my a/f was bouncing all over the place sitting at a stop light. It was going from 13.4 to 15.3 just sitting there. After 10 min or so it jumped back to 14.7 and showed a closed loop. It does this off and on during different times of the day.

My thoughts were the car is supposed to be in a closed loop unless under wot? My tune was done with HPTuner. Mods are 3.4,wizaired, plog, coated crossover, 104's, 3" catless dp, and zzp wires.

Thanks
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whitelightnin04MC
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PostPosted: Fri Dec 23, 2011 12:03 pm    Post subject:   Reply with quote

I remember something about a catalyst test that causes the AFR to continue to climb and the car uses the rear o2 sensor to determine if the cat is functioning. The test is something that's in the programming that you couldn't change without tiny tuner or doing something with the pcm's database. It's been a long time since I've messed with the powertuner. Hopefully I'm on the right track and someone will be able to help you out .

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chibiblacksheep
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PostPosted: Fri Dec 23, 2011 12:40 pm    Post subject:   Reply with quote

The car also stays open loop until it reaches operating temperature.

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nightryder
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PostPosted: Fri Dec 23, 2011 2:31 pm    Post subject:   Reply with quote

Are you verifying the AFR with a wideband? The AFR that shows up on the scan gauge is commanded AFR, not actual. How are you verifying that it's in closed loop? Is the car at operating temp when this happens?

IIRC the cat test happens randomly, and it doesn't need to be at an idle for it to occur. You need tiny tuner to disable it. This could be your problem, but I doubt it as it usually only dumps fuel (gets progressively richer). I don't think it will command open loop either, it shows up in the LTFT if i'm not mistaken.

Did you try resetting the trims to see what it does?

Can you send me your .hpt file again? I seem to have lost it.

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whitelightnin04MC
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PostPosted: Fri Dec 23, 2011 6:50 pm    Post subject:   Reply with quote

nightryder wrote:
Are you verifying the AFR with a wideband? The AFR that shows up on the scan gauge is commanded AFR, not actual. How are you verifying that it's in closed loop? Is the car at operating temp when this happens?

IIRC the cat test happens randomly, and it doesn't need to be at an idle for it to occur. You need tiny tuner to disable it. This could be your problem, but I doubt it as it usually only dumps fuel (gets progressively richer). I don't think it will command open loop either, it shows up in the LTFT if i'm not mistaken.

Did you try resetting the trims to see what it does?

Can you send me your .hpt file again? I seem to have lost it.


Very true. My LTFTs would go crazy, not the AFR.

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slowsol
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PostPosted: Fri Dec 23, 2011 6:53 pm    Post subject:   Reply with quote

nightryder wrote:
Are you verifying the AFR with a wideband? The AFR that shows up on the scan gauge is commanded AFR, not actual. How are you verifying that it's in closed loop? Is the car at operating temp when this happens?

IIRC the cat test happens randomly, and it doesn't need to be at an idle for it to occur. You need tiny tuner to disable it. This could be your problem, but I doubt it as it usually only dumps fuel (gets progressively richer). I don't think it will command open loop either, it shows up in the LTFT if i'm not mistaken.

Did you try resetting the trims to see what it does?

Can you send me your .hpt file again? I seem to have lost it.


Email address again....
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