Welcome to the North American Subaru Impreza Owners Club Monday December 22, 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 > Engine Management & Tuning > Open Source Reflashes

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 05-10-2013, 06:44 PM   #1
manys
Scooby Specialist
 
Member#: 265277
Join Date: Nov 2010
Chapter/Region: MWSOC
Location: Chicago
Vehicle:
2005 White
and pretty

Default -15% idle issues. Electrical gremlins?

What's up guys. I'll keep it short and on point as much as I can so it's easier to grasp for people who want to help me. Please post any questions below.


I had the car for 6 months. It had SlowBoy Racing 725cc Bosch injectors since the beginning and I always had problems with idle fuel trims.

A trim was always deep into -%(-10/15%) when B,C,D were - 3%

Besides that car was running great. OL fueling was on target, no knock. Did plenty of WOT pulls.

Few days ago car suddenly started knocking in low load and finally started breaking up under low load, I got 'System Too Rich' code and all fuel trims went -15%. Few hours later car suddenly started running LEAN this time. Idled 17:1 AFR and all the trims became +10/15%. few hours later idle fixed itself back to 14.7:1 AFR but A,B,C trims stayed at +10/15% even after long driving.

I checked many things next day and was left with injectors. Replaced those 725cc with stock 420cc's. I set stock 02 WRX latencys and together with stock MAF scaling went to drive the car. Everything is like it was before so A trim -14%, b and C -3%. BUT, when I turn on the fan(NO A/C, ac belt is disconnected,just the fan) car revs up and A trim stabilizes to -5%. Looks like electrical problem?? That didn't happen with 725's

Car idling and fan turning on:
http://s1016.photobucket.com/user/pl...ef1e5.mp4.html

Obviously my 725 injectors started acting up but now I confirmed that I have some issue with my idle. Because second set of injectors is behaving the same way except that now there's another issue with crazy behavior when I turn on the fan.



My questions: what are the possible reasons for large negative fuel trims at idle only?? And how can a fan cause such crazy rev change and fueling change??
* Registered users of the site do not see these ads.

Last edited by manys; 05-10-2013 at 06:50 PM.
manys is offline   Reply With Quote
Old 05-11-2013, 08:51 AM   #2
Larimer
Scooby Newbie
 
Member#: 205191
Join Date: Mar 2009
Location: Detroit, MI
Vehicle:
2006 Saab 9-2X Aero
Black

Default

Check for boost leaks.
Larimer is offline   Reply With Quote
Old 05-11-2013, 12:53 PM   #3
manys
Scooby Specialist
 
Member#: 265277
Join Date: Nov 2010
Chapter/Region: MWSOC
Location: Chicago
Vehicle:
2005 White
and pretty

Default

Quote:
Originally Posted by Larimer View Post
Check for boost leaks.
I did, no leaks.
manys is offline   Reply With Quote
Old 05-11-2013, 05:17 PM   #4
nmlittlebigman
Scooby Specialist
 
Member#: 321409
Join Date: May 2012
Chapter/Region: SWIC
Location: Arrey, NM
Vehicle:
2015 WRX LTD
WRB

Default

Maybe dirty or faulty IAC?
nmlittlebigman is offline   Reply With Quote
Old 05-12-2013, 07:30 PM   #5
BlazeRex
Scooby Specialist
 
Member#: 268354
Join Date: Dec 2010
Chapter/Region: NESIC
Location: Massachusetts
Vehicle:
02 WRX 05 LGT
Slow Automatics

Default

If there are no leaks, bad MAF or bad O2 sensor. If you have a wideband simly force the car into OL and watch what it reads.
BlazeRex is offline   Reply With Quote
Old 05-12-2013, 08:21 PM   #6
manys
Scooby Specialist
 
Member#: 265277
Join Date: Nov 2010
Chapter/Region: MWSOC
Location: Chicago
Vehicle:
2005 White
and pretty

Default

repaced a maf ,same thing. Replaced a fuel pressure regulator and checked fuel pressure. 37psi with vacuum hose connected and 47psi without.

o2 reads fine compared with wideband at idle. Remember I only have a problem at IDLE.

Maybe exhaust leak in the headers? MAF measured air would escape before reaching front o2 creating false rich condition so ecu would pull back fuel.


I also figured out that the rpm change caused by turning the fan on is normal with stock injectors. My brothers 07 wrx does the same thing.
manys is offline   Reply With Quote
Old 05-12-2013, 08:44 PM   #7
cosseywrx
Scooby Specialist
 
Member#: 276443
Join Date: Mar 2011
Chapter/Region: TXIC
Location: Abilene, TX
Vehicle:
2005 2.1 stroker WRX
OBP

Default

Rescale maf? Clean iacv? Fuel flow scaling?
cosseywrx is online now   Reply With Quote
Old 05-12-2013, 09:49 PM   #8
manys
Scooby Specialist
 
Member#: 265277
Join Date: Nov 2010
Chapter/Region: MWSOC
Location: Chicago
Vehicle:
2005 White
and pretty

Default

injectors,airbox, maf scaling,injector latencys/scaling are all stock so I shouldn't touch the maf or injector scaling to fix the problem.

I'll clean the iacv although I don't see the correlation to my problem.
manys is offline   Reply With Quote
Old 06-17-2013, 03:34 AM   #9
manys
Scooby Specialist
 
Member#: 265277
Join Date: Nov 2010
Chapter/Region: MWSOC
Location: Chicago
Vehicle:
2005 White
and pretty

Default

I'll update the thread for people searching for answers for similar questions in the future:

I installed brand new five-o 1000cc's and was able to tune everything out pretty easily.

Idle, cruise, and D range are all nice now +/- 2%
manys 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 04:52 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.