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Discussion Starter #1
Hey Guys,

There seems to be a infinite amount of threads talking about AF Learning 1 values and I've tried to read them all. It seems like there are two areas of thought.

1) The AF Learning 1 values should be +-8%. Anything over this indicates there is an issue that needs to be fixed.

2) The AF Learning 1 values can vary greatly, however, you only need to worry if its NOT 0 at WOT.

I recently replaced my turbo and did a retune to stage 2 91 octane. I have a downpipe and exhaust. Today when I pulled into my driveway, in park, I was reading -22.66 with AF Learning 1. Is this normal? When I really step on it (WOT), AF Learning returns to 0 but anything other then wide open throttle has negative values. Maintaning speed shows -10.

Following the first stage of thought I definitely have a problem. The second stage of thought would indicate I can ignore everything since my values are zero at WOT. What your guys opinion? A -22 to 0 range seems quite large.

I currently have just over 80,000 miles and have ordered a new MAF, inlet 02 sensor, and exhaust sensor. I hate to throw parts at it but I figure now is a good time to eliminate some possibilities.

Thanks for any info!
 

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Discussion Starter #2
I'm checking my turbo inlet as well. Seems like there is a slight bunch of the rubber at the turbo. Could this be a location for a leak? I don't have a test setup for leaks.
 

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2001 Forester STi 6spd with MapDCCD
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Hey there Vander,

So if you arent already aware, there are 2 main learning systems with fuel to watch for in these ecus.

The AF correction #1

The AF learning # 1

The AF correction is a real-time view into what correction is being applied where in the lower load ranges (they dont apply in WOT for newer 08+ models) and the AF learning is an overview of its 4 sub-categories.... Learning ranges A, B, C and D. The letters dictate load ranges in which different learning's may be applied. Range A is for idle, B is for low throttle cruise, C for mild throttle cruise and D is the last range applied before entering into open-loop for WOT performance. Watching AF learning 1 will flux as it passes through each range, so sometimes it helps to do live view (snap shots) of all 4 ranges to get an idea of where a problem could lie.

So, if you are seeing a 22% reduction in fuel at idle, that could indicate an issue such as simple as a very clogged air filter or dirty'd-up MAF sensor needing some cleaning (with MAF specific cleaner). On the more advanced side of that issue, it could also indicate the start of a pre-turbo exhaust leak forming somewhere in the header or uppipe when you see values start to dive extra rich like that. Its hard for me to actually diagnose without seeing the car in person, but from my experience with heavy negative values in stock form, i had often traced it back to those things on clientele vehicles that I have had to troubleshoot before actually tuning them. Also, your general location and climate plays a factor too. If you live close to a mile or more above sea level, you may see some decent swings in the learning values, esp if you travel between wide ranges of altitudes.

I'd say start with the basics here. Clean the MAF (or replace as i see you have one ordered) , replace the panel air filter, perhaps throw some injector cleaner through the system too if that has not been done in awhile. It also wouldnt hurt to do a set of new spark plugs if you dont know the history of whats in there. Start with a fresh tune-up here and report back and see if the values improve a bit.
 

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Discussion Starter #4
Hey there Vander,

So if you arent already aware, there are 2 main learning systems with fuel to watch for in these ecus.

The AF correction #1

The AF learning # 1

The AF correction is a real-time view into what correction is being applied where in the lower load ranges (they dont apply in WOT for newer 08+ models) and the AF learning is an overview of its 4 sub-categories.... Learning ranges A, B, C and D. The letters dictate load ranges in which different learning's may be applied. Range A is for idle, B is for low throttle cruise, C for mild throttle cruise and D is the last range applied before entering into open-loop for WOT performance. Watching AF learning 1 will flux as it passes through each range, so sometimes it helps to do live view (snap shots) of all 4 ranges to get an idea of where a problem could lie.

So, if you are seeing a 22% reduction in fuel at idle, that could indicate an issue such as simple as a very clogged air filter or dirty'd-up MAF sensor needing some cleaning (with MAF specific cleaner). On the more advanced side of that issue, it could also indicate the start of a pre-turbo exhaust leak forming somewhere in the header or uppipe when you see values start to dive extra rich like that. Its hard for me to actually diagnose without seeing the car in person, but from my experience with heavy negative values in stock form, i had often traced it back to those things on clientele vehicles that I have had to troubleshoot before actually tuning them. Also, your general location and climate plays a factor too. If you live close to a mile or more above sea level, you may see some decent swings in the learning values, esp if you travel between wide ranges of altitudes.

I'd say start with the basics here. Clean the MAF (or replace as i see you have one ordered) , replace the panel air filter, perhaps throw some injector cleaner through the system too if that has not been done in awhile. It also wouldnt hurt to do a set of new spark plugs if you dont know the history of whats in there. Start with a fresh tune-up here and report back and see if the values improve a bit.

Thanks for the information!!!

After installing the new MAF, turbo inlet pipe, and process west verticooler, my AF Learning 1 values have stabilized.

Another thing i removed was the K&N Filter. I've heard the oil from the K&N filter can mess up the MAF so i went back to stock. I don't want to play games with my new MAF haha

As you said, I must have had either a bad MAF or leak in the intake track. I kind of wish I would have installed these not all at once because now I don't truly know what the source of the problem was. Either way she seems to drive alot better now!
 
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