Welcome to the North American Subaru Impreza Owners Club Tuesday September 30, 2014
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Here you can view your subscribed threads, work with private messages and edit your profile and preferences Home Registration is free! Visit the NASIOC Store NASIOC Rules Search Find other members Frequently Asked Questions Calendar Archive NASIOC Upgrade Garage Logout
Go Back   NASIOC > NASIOC Technical > Pre-2002 Factory Turbo Powertrain

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads.
Reply
 
Thread Tools Display Modes
Old 10-11-2012, 11:12 AM   #1
simer1228
Scooby Newbie
 
Member#: 171039
Join Date: Feb 2008
Chapter/Region: NESIC
Location: Burlington, Vermont
Vehicle:
99 RSTi Type-R LTD
Black Diamond Pearl

Default Lean A/F ratio's all of a sudden [solved]

I noticed this morning as I was warming my car (99 RS w/ v5 EJ207) up, it was skipping a bit at idle. I just knew it didn't sound right and lo and behold, my car is idling at 17:1 when it should be around 14.7 +\- 1.0. I thought hey, maybe if I just start driving, it'll work the kinks out ...wrong! Ratios seemed normal under boost but at cruise it was still lean. Soooo I richened the mixture up via the commander and gently drove her back home.

I didn't get to take a look as I was on the verge of running late for work but I'm confident my AEM wide band o2 is accurate as its only a few months old.

I'm hoping that its just a vacuum leak or a dirty MAF sensor. If not, I'll toss my factory ECU in and see if that fixes the issue.

Does anyone have any ideas, other than what I already posted, why overnight my car would run lean?

Turned out to be a bad primary o2 sensor.

Last edited by simer1228; 10-12-2012 at 08:36 PM.
simer1228 is offline   Reply With Quote
Old 10-11-2012, 12:30 PM   #2
TommyAtomic
Scooby Newbie
 
Member#: 257043
Join Date: Sep 2010
Chapter/Region: VIC
Location: Vancouver BC
Vehicle:
1993 JDM WRX Wagon
Black

Default

Dirty or defective MAF is possible but if it happened all of the sudden I would definitely not swap ecu's. Troubleshoot the problem you actually have.

I would bet on preturbo leak. Unmetered air. Could be an old cracked pcv hose or bad clamp.

Your location says vermont. I bet its starting to get pretty cold at night there. Old rubber hoses will absolutely crack from drastic temperature changes. Changes such as hot engine bay vs cold night air.

Dont make your initial troubleshooting more complicated than the actual problem.
TommyAtomic is offline   Reply With Quote
Old 10-11-2012, 12:56 PM   #3
simer1228
Scooby Newbie
 
Member#: 171039
Join Date: Feb 2008
Chapter/Region: NESIC
Location: Burlington, Vermont
Vehicle:
99 RSTi Type-R LTD
Black Diamond Pearl

Default

Thanks TomTom. When I get home this afternoon, I'll check the inlet as last night was the coolest it's been this month. Hopefully it's something simple like an air leak.
simer1228 is offline   Reply With Quote
Old 10-11-2012, 05:38 PM   #4
simer1228
Scooby Newbie
 
Member#: 171039
Join Date: Feb 2008
Chapter/Region: NESIC
Location: Burlington, Vermont
Vehicle:
99 RSTi Type-R LTD
Black Diamond Pearl

Default

Didn't find any obvious leaks and I cleaned my MAF for the hell of it. Started it up and it idled and warmed up normally, with the as usual, slightly rich a/f ratios, just like it always has. But once the water temp got just above "C", I watched the a/f ratios lean right out to 17ish. RPM's also takes longer than usual to settle to idle.

I poked around the engine bay with some starter fluid and still couldn't conclude that I had an air leak.

Ideas?

Last edited by simer1228; 10-11-2012 at 05:51 PM.
simer1228 is offline   Reply With Quote
Old 10-12-2012, 10:17 AM   #5
sonic rex 03
Scooby Newbie
 
Member#: 62313
Join Date: May 2004
Chapter/Region: Tri-State
Vehicle:
2003 16G 38mm ewg
sonic yellow

Default

Did u check your o2 sensor operation?
sonic rex 03 is offline   Reply With Quote
Old 10-12-2012, 08:35 PM   #6
simer1228
Scooby Newbie
 
Member#: 171039
Join Date: Feb 2008
Chapter/Region: NESIC
Location: Burlington, Vermont
Vehicle:
99 RSTi Type-R LTD
Black Diamond Pearl

Default

Turned out to be a bad primary o2 sensor.
simer1228 is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -4. The time now is 08:23 AM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2014 Axivo Inc.
Copyright ©1999 - 2014, North American Subaru Impreza Owners Club, Inc.