A/F Correction - What is normal and not?

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A/F Correction - What is normal and not?

Postby Shaheenis » Thu Nov 22, 2018 4:01 pm

Hi there,

Just been doing some logging in an effort to diagnose worsened fuel economy and an issue where my engine decides to rev for no reason occasionally when I am idling at lights. The revs might jump 500rpm from idle and sit there until I blip the throttle or they come down of their own accord many seconds later. The car otherwise drives find and seems to accelerate smoothly and boost.

Looking at the logs from a sedate drive home in 'I' mode I can see my A/F Correction maxes at 18.75% and drops as low as -22.66%. Is this normal?

The LV guide that BBB posted at this link (https://flic.kr/p/nQtb8N) suggests anything over +/- 15% in LV is an issue but is that percentage different from the raw data I am seeing in Romraider?

Any help or advice appreciated.

Regards,

Tim
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Re: A/F Correction - What is normal and not?

Postby bigBADbenny » Thu Nov 22, 2018 7:31 pm

Sorry I'm not expert enough to answer that, but I'd say go by how your LV looks as its a relatively universal standard.

Done the usual things like cleaned the airfilter, maf, UEC & injector cleaner?

Have you logged the issue specifically?
If not, make a log at idle, let the car "fix" the idle by itself, then if it does "it" again, correct it with a blip.
Post a link (dropbox, google drive or wetransfer etc) and I'd be happy to take a peek.

I guess in terms of parameters, you'd want the usual tuning parameters including fuel pump duty, neutral position switch, open/closed loop, throttle angle and my favourite: l&r vvt angles.
Other than a mechanical fault related to the above, I'd have to say the usual suspects for an unstable idle are related to vacuum leaks.

You can quickly check the boost side with generous sprays of water and diluted detergent in a trigger bottle whilst an assistant revs the car. Same for the exhaust, on a cold startup.

Inlet side post maf, pre-turbo is a bit trickier, I made a tyre compressor driven, paint can accumulator, diy smoke/bubble tester. Use a strong torch to spot the evidence, starting around 1psi. Read the diy's so you're not popping your cam seals...

Here's a comprehensive guide, iirc at 1 psi just remove the oilcap. https://turboboostleaktesters.com/how-t ... -a-subaru/
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Re: A/F Correction - What is normal and not?

Postby Shaheenis » Thu Nov 22, 2018 9:39 pm

Thanks Ben.

Yes I had just performed a minor service - EUC, oil flush, oil change, oil filter and injector cleaner. MAF and filter cleaned less than 12mths ago but mine rarely gets dirty.

I have had the fluctuating revs issue before and always seems to come on after an ECU reset/flash but sometimes it just comes on for no reason. Today as an example it hasn't happened.

I will take a targeted log as you have suggested when I get a chance. For now I have linked an LV from tonight which to me looks fine.

https://photos.app.goo.gl/5wJvc6DQqFyBFx1cA

https://photos.app.goo.gl/LUVLoGbYpbTaYDZf9

Cheers,
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Re: A/F Correction - What is normal and not?

Postby bigBADbenny » Thu Nov 22, 2018 9:46 pm

How old is the tune?
I remember Matt’s tune, ages and ages ago, would do that.
I probably get him to look at my tune annually, but that revs issue was 5 years ago iirc.
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Re: A/F Correction - What is normal and not?

Postby Shaheenis » Fri Nov 23, 2018 2:36 pm

I have just re-flashed to a V7 tune which was provided March this year. Prior to that I was running V6 from 2015 where the issue also developed. I ran the V6 tune for a very long time without any economy issues or rev issues and then it happened following an EUC and LV reset. Suffice to say if it is tune related, I am not sure why it isn't happening all the time.
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Re: A/F Correction - What is normal and not?

Postby bigBADbenny » Fri Nov 23, 2018 9:03 pm

How’s that log coming along :P
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Re: A/F Correction - What is normal and not?

Postby alexeiwoody » Sun Nov 25, 2018 5:11 pm

Shaheenis wrote:The LV guide that BBB posted at this link (https://flic.kr/p/nQtb8N) suggests anything over +/- 15% in LV is an issue but is that percentage different from the raw data I am seeing in Romraider?


Very simple answer - you're referring to AF corrections in RomRaider and LV shows AF Learning, they're different parameters. AF Learning is the more permanent, hence the name "Learned", correction - and what you want to keep under +/-10%.

On one of the log screenshots your VVT max angles seem a fair bit different, probably needs a more thorough look.

Your LV looks fine, so start by cutting out the other potential options first, before you dive into engine/tune issues (there are far too many). Check if it's A/C or temperature (whether your car is still cold, or the weather) related, etc.

Don't pay attention to how the car behaves after an ECU reset - this is the car in learning mode, and can do a bunch of things that it wouldn't normally. You need to pay attention only to what it does after it's already learned and is supposed to be in "normal" mode.
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Re: A/F Correction - What is normal and not?

Postby bigBADbenny » Sun Nov 25, 2018 6:53 pm

Awesome! ^ :good:
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Re: A/F Correction - What is normal and not?

Postby Shaheenis » Sun Dec 09, 2018 8:12 pm

Thanks Alexei that is helpful. I have been having a problem with romraider logger working only intermittently so I haven't taken any logs yet. The car is driving well otherwise and that increased idle can not be there for a day or two and then it will do it every time I idle at lights on other occasions. I took a decent drive the other week and fuel economy came back down into the 12s so the economy issues are definitely related to all my short trip city driving at least in part.

Has anyone had the issue with Romraider logger where it rarely actually connects to the ECU? I replaced the cable and tried different laptops and same thing. Sometimes it will connect and 'read data' but most times it just sits there saying 'ECU init - trying to connect to ECU' or something similar.

Cheers,
Shaheenis
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Re: A/F Correction - What is normal and not?

Postby bigBADbenny » Sat Dec 15, 2018 7:26 am

Grab a cheap android with otg and use Btssm ;)

It could be that the solder on the tactrix USB port has gone flaky.

If so, I’d hot glue a short extension to the plug case: preferably with a right angle mini usb, at the right angle to get a good connection.

Or get the port resoldered by a pc doctor...
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