I don't see how a header crack would affect your idle. The O2 sensor measures the A/F *ratio*, so even if there is a leak the ratio stays the same. But.. I hope it fixes your problem, and if it does I would like to know how.

At idle, you could easily draw atmosphere into the exhaust and then push it into the 02 sensor on the next pulse.

Negative pressure in the header/uppipe before the turbo? Even at idle - I dunno about that. Again - I hope it fixes it.

I'm putting my stock headers on tomorrow. I will probably let C and C weld the crack, then I might either heat wrap or spray paint them with black heat paint. I will post some pics and let you know if it works, praying that it works.

I'm stumped. I swapped my headers and put on new gaskets, but the idle problem is still there. Here is what C and C checked:
-smoke tested for vacuum leak
-fuel pressure regulator check
-MAP and MAF test
-O2 sensor check
-ECT and IAC tested
-Checked emmisions, ok when running, but very lean at idle, causing rough idle.

What next? fuel injector cleaner? try swapping to a stock air box?(don't know why this would be the problem, since I have been running 50k plus miles with the same intake). Get a retune? I tried switching maps, but no effect. Where do I go from here???

there is something that we didnt try here

.... if its the reason ill be really pissed off.

call me tonight and we can test for it.

the reason im not saying what it can be is because i would be embarressed we didnt try it first.

Did you put the stock Uppipe back as well?

Plug your AP cable into a laptop and dashboard/log with Enginuity.

You will probably find it hunting A/F, but maybe not.

Try the stock air box.

Flash it back to stock

Take it to Subaru

Tighten the gas cap? :lol:

I searched online for enginuity, but the website doesn't work. I no longer have a air box, but would be willing to try one if anyone has one laying around. The next thing is taking it to subaru. Phil recommended trying a differnt bov, since only idle running condition is lean.

Just for you...

ftp://benzfamily.gotdns.com/download

yeah we need a stock BPV. if anyone can let us use theres even for 10 minutes i really think this option has a shot at fixing it.

to PM either me or Ddubs and let us know if you can help us for a short time tonight or soon.

thanks

can't get the link to work.

Fixed the link above.

And you don't need a BOV, just pinch the vacuum hose and put a plastic bag over the return nipple and put the hose back on. That should eliminate it at idle.

You could probably just stick a couple fingers/thumbs in the holes/hoses for a minute too. (That's what she said)

I just checked all the vacuum hoses that enter the intake. When plugging them with my finger, none of them affect idle. The BOV vacuum hose does not effect idle either. I didnt try plugging the actual recirc hose that enters the intake from the BOV, but I don't know if that would effect idle. Could a faulty spark plug give a P0171 code? (I think it would throw a misfire code) It all started from the MAF sensor, but even a new one didn't fix that??

Dean, it won't allow me to download enginuity, I can get to the file though. Thanks for the link

Anyone have a stock air box laying around? I don't know what to do from here :?:

Fixed for real this time...

You can always dl Tari ECUExplorer as well.

This is a long shot...

Is this the first time you've cleaned the MAF since the tune? Maybe it was tuned with a dirty MAF and a clean/new one screws it up.

What size injectors?

the injectors are stock. My car got tuned about 3yrs ago. I tried switching between different maps to idle check with no luck. If the MAF was dirty this whole time, more air would be flowing by that the sensor wouldn't pick up. Wouldn't the O2 sensor have sensed a lean running condition?

I got enginuity to work. I was looking at the A/F ratio graph. Once you let off the gas and let it idle, A/F ratio jumps up(engine stumbles), takes a few seconds to recognize, then falls back down. What is normal idle A/F ratio? the reading was around 16=lean compared to stoichiometric 14.7.

I really want to try a stock air box. If someone is willing to swap with me just to check, i'll buy you beer :)

The idle AFR should be 14.7:1 +/-.3. If yours is idling at 16:1 then I would log your fuel trims at idle - short and longterm, and see what those are doing.

Just as a general note... normally when you let off the gas the AFR will spike up (lean out) as the engine falls in rpm with no load. But it should settle around 14.7:1.

I am 80% sure I have an extra airbox in storage. You can use it as long as you need it. I won't be able to make the meet tonight, but I live in NW Reno and would put in on my porch if I'm not there. PM me for my number.

if noone steps up to this, im bringing my wrenches to the meet tonight and stealing someones BPV, to see if it fixes it.

it meets all the of the criteria of his problems.

it just doesnt make sense why it would fail.

I have a stock STI BPV also that can be borrowed...

bingo.

As has been said, it should hover at 14.7 at idle. 16 is out of bounds. What were the learned and immediate A/F corrections running at.

Hunting only at idle can only be a few things.

Leak somewhere between the MAF and the O2 sensor.

Bad intake map.

Bad MAF or O2 sensor.

If the BOV is bad, pulling it and blocking all the holes should fix the issue at idle.

I have an after market BOV & plug you can try.