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Old 09-10-2012, 06:13 PM   #1
myk
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Default AFR off at idle (warm) after TGV delete.

Deleted the TGV's while I was fixing my block, got everything running again and I'm seeing a slightly higher AFR at idle then I did before. Even after warmed up, under any amount of throttle it goes to it's 14.7-14.9 range but just sitting there it will wander up to 15.4-15.7. Cruising it is hitting all it's AFR targets and even on WOT, though I think I would be in closed loop fueling under those conditions.

Aside from a lack of TGV's (which I went ahead and ported to) I have a silicone inlet and high flow filter.

Vacuum isn't oscillating or idle, going to look for some leaks though anyways.

Think I might need to adjust MAF scaling to account for the inlet + TGV's? My other guess is that it is the primary o2 since it is only acting weird in open loop fueling.

Just wondering if anyone else has had this issue, searched around and have not found anything conclusive.
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Old 09-10-2012, 07:37 PM   #2
biodude
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My TGV deletes drove me nuts, as good as I thought I sealed my TGV's I still had a leak on one of em.

Last edited by biodude; 09-10-2012 at 07:43 PM.
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Old 09-10-2012, 08:09 PM   #3
myk
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Quote:
Originally Posted by biodude View Post
My TGV deletes drove me nuts, as good as I thought I sealed my TGV's I still had a leak on one of em.
Yeah, going to check for leaks when I get off work here. I was impatient and didn't weld these just did the set screw/rtv methed. Have a second set I am doing for a friend that I am welding up, might just pull mine and do them right.
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Old 09-10-2012, 08:25 PM   #4
the suicidal eggroll
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Little expensive, but these work very well and don't require any welding/sealing:
http://www.kstech.biz/servlet/the-16...ete-Kit/Detail
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Old 09-10-2012, 10:44 PM   #5
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check your inlet connection too. maybe its not on fully or something, I would think you'd have to be sucking quite a bit of unmetered air to be lean at idle.
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Old 09-11-2012, 12:37 AM   #6
myk
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Quote:
Originally Posted by the suicidal eggroll
Little expensive, but these work very well and don't require any welding/sealing:
http://www.kstech.biz/servlet/the-16...ete-Kit/Detail

I was considering those, but I have access to a tig for free.

Checked for leaks by spraying brake clean around the tgv's and got no change in idle. Going to do a proper leak check when I have some day light with a boost leak checker.

I did run the car a little harder and let it get above 160 degrees and it brought the afr down to 15.

The engine is running a 10-20 degrees cooler then it was last time it was in.

Running one step colder plugs, not sure if it makes a difference?

Have a brand new OE o2 otw (denso off Amazon) since mine looks like it has seen better days lol.
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Old 09-12-2012, 12:22 PM   #7
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Your getting lean surge because there is more air at idle than before. you need to tune it out.
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Old 09-12-2012, 12:53 PM   #8
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When I did tgv deletes on my 05 sti it ran identical to before I installed them. My wideband showed the same afr before and after the install. I think you are on the right track looking for leaks. If there's no leaks adjust the maf. Sounds like you already know what to do.
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Old 09-12-2012, 01:14 PM   #9
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Quote:
Originally Posted by stu View Post
Your getting lean surge because there is more air at idle than before. you need to tune it out.
With a MAF, that doesn't make sense. If there's more air, then the MAF will read more air and will add fuel for it. What you said only applies to speed density tunes.
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Old 09-14-2012, 12:59 AM   #10
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Quote:
Originally Posted by the suicidal eggroll

With a MAF, that doesn't make sense. If there's more air, then the MAF will read more air and will add fuel for it. What you said only applies to speed density tunes.
Unless I'm sucking air post maf, just picked up my buddies boost leak tester so we'll find out. Haven't had a chance to look at my afr correction values either. I guess depending on how high that is it at idle it can indicate a vacuum leak.


Soooo busy lately
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Old 09-14-2012, 01:06 AM   #11
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Quote:
Originally Posted by myk View Post
Unless I'm sucking air post maf
Right, a leak changes things, and could definitely cause the problems.
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Old 09-16-2012, 02:57 AM   #12
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Welp, no luck in finding a leak yet. Hear a tiny whistling sound under 20 psi somewhere but am doubting that a leak that small would cause my afrs to be fluctuating as much as they are. Still waiting on a primary o2, hope that fixes my issue.
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Old 10-05-2012, 02:18 AM   #13
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So replaced the front o2 and fuel filter, afrs are still out of wack at idle. Unplugged and ran no maf, afrs still ****ty. Cleaned it and the same result.

Lower the idle gets as the car warms up the leaner it becomes. Seems like it's been getting worse, I'm seeing values as high as 18 now.

Thinking the wideband might be fubar, it's a Bosch unit with only 2k miles on it though :/. Going to test it out tomorrow and see.

Going to put a fuel pressure gauge in as well to see if the fpr isn't messed up.
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Old 10-06-2012, 01:32 AM   #14
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Quote:
Originally Posted by biodude View Post
check your inlet connection too. maybe its not on fully or something, I would think you'd have to be sucking quite a bit of unmetered air to be lean at idle.
Actually, it takes very little unmetered air to completely change your idle. At idle my engine pulls about 3 g/s, so an extra 0.3 g/s would be a 10% difference, or enough to go from 14.7:1 to 16.2:1. But cruising at 30 g/s, the same 0.3 g/s leak is only 1%, so 14.7:1 only turns into 14.85:1. Realistically the leak would probably get a bit worse but it still pretty minor compared to how much metered air is coming in.

When someone says their idle is screwed up but the runs fine in cruise, vacuum leak is usually the culprit. Not always, but usually.

MYK: Before you replace you wideband, hook up a laptop with RomRaider, or an AccessPort, and compare the WB AFR to the stock sensor's AFR.

And while you have the laptop hooked up, check your AF Correction A-D values. With a vacuum leak, A will be +15% and the others will be closer to zero.
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Old 10-06-2012, 02:35 AM   #15
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Am I the only one not seeing why lean idle is a bad thing? I would do 2 things, check your MAF reading, check your inlet tube connection to turbo make sure you got it on all the way, if those are good check your injector duty cycle/pulse width and fuel pressure. If everything is fine it would easily be tuned out. The question then is why not run it leaner at idle if your are hitting target idle speed? Why waste fuel at idle. As long as your Pyrometer/EGT readings are within spec its really just more efficient to run it lean at idle.
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Old 10-08-2012, 11:38 AM   #16
myk
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Quote:
Originally Posted by NSFW

Actually, it takes very little unmetered air to completely change your idle. At idle my engine pulls about 3 g/s, so an extra 0.3 g/s would be a 10% difference, or enough to go from 14.7:1 to 16.2:1. But cruising at 30 g/s, the same 0.3 g/s leak is only 1%, so 14.7:1 only turns into 14.85:1. Realistically the leak would probably get a bit worse but it still pretty minor compared to how much metered air is coming in.

When someone says their idle is screwed up but the runs fine in cruise, vacuum leak is usually the culprit. Not always, but usually.

MYK: Before you replace you wideband, hook up a laptop with RomRaider, or an AccessPort, and compare the WB AFR to the stock sensor's AFR.

And while you have the laptop hooked up, check your AF Correction A-D values. With a vacuum leak, A will be +15% and the others will be closer to zero.
Did that the other day and none of the corrections were pegged. If anything they looked like they would. The stock o2 sensors calculated afr in romraider was bouncing around 14.7 like it should. Not seeing an exhaust leak before the wO2. Just weird the wideband reads correct above idle.

I know you can pull them out and do the trick with the brake clean and rag to test them so I suppose that's next.
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Old 10-08-2012, 02:55 PM   #17
myk
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Might just be the maf scaling is off a hair, people say tvg porting and removal wouldn't change anything but what about in combination with an inlet install?

Also the idle readings are at 20+ now and it's idling the same it was before.
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Old 10-09-2012, 05:05 PM   #18
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^^^^ I read somewhere on here where a lean idle causes more emission pollutants.........
A leaner idle may not pass the "sniffer"....for those that are concerned with passing state emissions and all that jazz.
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