Here is what I KNOW:

1)Learn control is OFF in open loop mode.

2)Learn control is OFF during WOT.

BLM's and Integrator are locked at 128 when learn control is OFF. I think this is normal. But the O2 volts were still fluctuating (in closed loop). So, when NOT in the above modes, what would cause learn control to go off? Highwaymode? I don't think I was in highway mode, since my O2 volts were still bouncing, and mostly on the rich side.

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Best ET 14.413 @95.57 without
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Also with stock 2.77 rear end!!!

 

Well if you think about it there's nothing to "learn" when you're in open loop (WOT or cold start). When in closed loop however the ECM tries to "learn" the best fuel and timing values while you're driving. Open loop values are dictated by what values are stored in the prom and they cannot change. This isnt a very good explanation, so hopefully Trax or Glenn will have something to add

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92 Z28 5.7
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TES headers, Flowmaster catback, MSD ignition, #24 SVO injectors, 1LE aluminum driveshaft.

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A soft harware failure can do that, ie bad MAF. Some failures are marginal and not serious enough to turn on the SES light.

 

Yes, going into Highway Fuel Mode causes learn control to be turned off. Going into Power Enrichment Mode also causes it to be turned off, which is probably what you were in since you were running more rich than lean. You'd definitely be lean if you were in HFM.

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Greg Westphal
'87 IROC 305TPI/A4

 

Thanks for all your replies. I doubt that my MAF sensor is bad, car has only 57k on it now. I did have a relay go bad though. Just what is the Power Enhancement mode? I see it alot with speed density cars, but I don't see it with MAF cars.

I am going to do a scan on my ride into work tuesday, just taking a normal drive in to see how the numbers look. I lowered some of the values for highway mode, so I am quite interested to see if this mode comes up. I will also pay close attention to the BLMs and Integrator, since I think it runs on the rich side.

 

Power Enrichment is when you step on the gas. It goes into effect above 50-80% depending on what rpm you're at and what your bin has those values set at. It's also known in TunerCat as WOT, but you can go into PE way before hitting 100% TPS.

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Greg Westphal
'87 IROC 305TPI/A4

 

I've seen my learn control turn off for short times while I'm still in closed loop. It appears when driving at a relatively constant speed with little throttle. It seems to occur when an EGR test would be done.

I have the EGR blocked, the EGR error code disabled, and the EGR set to never turn on. I don't know if the learn control is turned off during the test, or if it has to do with failing the test, but the conditions when it occurs are when a test would be done.

Joe
92 Z28 13.3@102