[SOLVED] P0171 - System too lean

[Kimmo]

So I've got the flashing S and cruise lights, plus check engine, BtSsm says from this:

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Should I reset the ECU? There's also this:

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[bigBADbenny]

Boost leak maybe.

Bring it over and I’ll inlet pressure test it.

In the meantime do a visual inspection, also check the FPR is still hooked up to the nipple at the base of cyl4 inlet manifold runner.

[bigBADbenny]

As you can see, it’s a stored code, but you have major fuel corrections currently and a little low load knock.

Intriguingly the IAM is still at 1.0, which suggests its kinda coping ok, off boost at least.
I wouldn’t be using any boost atm till you get it sorted.

What rpm is warm idle?

When was the ecu last reset?

[bigBADbenny]

#ynansb = you need a new short block lol.

Hopefully you got the Btssm kit in time.

How’s the driving experience been recently, compared to when you got the car?

Are there any driving symptoms apart from eg excessively rich exhaust?

[Kimmo]

What's the IAM?

I think it's idling at about 800, but it's a little rough.

How can I tell when the ECU was reset?

#ynansb - nice one. Any idea how to find out what it really means?

Haven't been using BtSsm cause without the right adapter, the phone doesn't have anywhere to sit - this is all the info I have. Why do you say, in time?

The only difference in driving I've really noticed, aside from no cruise or modes and the fuelly exhaust and the rough idle, is a weird twitchy throttle in third gear; just pootling around, trying to be smooth, it gets a bit jerky between slight acceleration and trailing throttle, and the economy meter jumps around as if the e-throttle has some crazy ideas about how to deliver the smoothness I'm asking for... That's a bit odd. Haven't noticed anything else.

I'll check out the rest of the stuff you mentioned and confirm what I'm saying from memory after a coffee. Wanna PM me your number so we can tee up your kind offer of a pressure test?

[Kimmo]

Yeesh - just did some logging when I went for a coffee... seems like the AFR sensor has a ceiling at 20.3, and I'm all over it

Is there a workaround for attaching CSVs? I tried tacking on TXT and JPG extensions, no dice. Maybe we can get @Ric to change the attachment restrictions?

Hm, can we even do mentions on this board?

Here are the CSVs, link expires in a week: https://we.tl/t-5jZWleZCVZ

Damn USB jack on the BtSsm phone is a bit sketchy; it disconnected when I bumped it.

Oh hey, the airbag light came on for a bit before going out again too.

[Kimmo]

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RPMtoAFR.jpg (64.09 KiB) Viewed 4678 times

[Kimmo]

In the meantime do a visual inspection, also check the FPR is still hooked up to the nipple at the base of cyl4 inlet manifold runner.

You mean via this little hose? Looks okay...

20201213_091015.jpg (78.57 KiB) Viewed 4678 times

The FPR is a tiny little thing, took me a bit to find it. And OMG, is that really my starter motor (not pictured)? Looks like it belongs on a motorbike!

Still haven't discovered where the throttle body is hiding... it's a jungle in there.

[Kimmo]

Lol, found it - complete with actual red flag attached!

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[Yowie]

Is that the hose to the PCV fitting on the manifold?

If so, that one got me once - super lean idle and error codes.

[Kimmo]

Is that the hose to the PCV fitting on the manifold?

If so, that one got me once - super lean idle and error codes.

BOV hose. It's a GFB one, hence the non standard ziptie... wonder if it was ever on properly; wasn't that easy to get back on all the way. Previous owner might've given it a yank when he refitted the standard BOV for RWC, or I might've when I reinstalled the GFB one.

In other news, still have an intermittent airbag light... no clue what that's about.

[bigBADbenny]

The airbag light is completely normal when using an obdii plug.

Its a factory feature so subaru techs don’t leave their scanners in the car after service.

Afr 20 is simply fully lean eg engine on the overrun, engine pumping air mainly.

I’ll peep the logs now...

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Nothing much to see here, the car was logged only for a short time off boost.

If you think thats the main issue solved, stay off boost for the next day or two, make an LV at the end of each day to see how fuel corrections are responding, hopefully for the better.

When making general diagnostic logs, keep logging on for longer, 5-15 minutes, as a bigger dataset is probably more useful.

Do try MegaLog Viewer, there is a free version.

The paid version opens up scatter graphs which are very cool, but its gonna cost ya

[bigBADbenny]

Also you need to be logging a/f learning 1.

Plus some other tuning parameters.

It can’t hurt to variously and temporarily turn on other parameters eg avcs vvt angles and misfires.

Check the Romraider faq for what and why to log certain parameters

[bigBADbenny]

And the graphed log ^ reveals you have no effective inlet vacuum

Hopefully it’s a log pre fix yeah?

[Kimmo]

Oh yeah, now I remember, the brake pedal was also sinking under my foot...

Those logs are all pre fix, yeah. Tried to take some more, but the connection to the phone keeps dropping out with the cable waving around and the phone in a cup holder. Was gonna see what I'd managed to gather, but was pretty busy yesterday.

Looking forward to getting a proper connection happening and the phone stuck semi permanently in place...