Welcome to the North American Subaru Impreza Owners Club Tuesday November 19, 2019
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Go Back   NASIOC > NASIOC Technical > Factory 2.0L Turbo Powertrain (EJ Series Factory 2.0L Turbo)

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.







* As an Amazon Associate I earn from qualifying purchases. 
* Registered users of the site do not see these ads. 
Reply
 
Thread Tools Display Modes
Old 11-01-2019, 01:23 PM   #1
Easyy
Scooby Newbie
 
Member#: 507940
Join Date: Nov 2019
Chapter/Region: MWSOC
Location: WI
Vehicle:
2002 wrx
white

Default Lean afr/bad idle, cant figure out why.

I just bought my wrx last Saturday and ive been having an issue that I cant seem to figure out.

At idle my afr gauge (passport) reads an afr of 17 and the idle sounds lopey. Car is running a OTS stage 2 tune from cobb and has a bigger tmic, catted downpipe, stock bov, stock intake.

When I unplug the MAF the idle goes back to 14.7. I bought a new denso MAF and that did not fix my issue.

I tried checking everywhere for vacuum leaks and I cant seem to find any. There is also a CEL for a misfire on all 4 cyls and fuel system lean.

Once the car is moving everything is normal, afrs read between 13 and 15 cruising.

Any ideas? I'm at a loss.
Car is a 2002 with 132k
* Registered users of the site do not see these ads.
Easyy is offline   Reply With Quote
Sponsored Links
* Registered users of the site do not see these ads.
Old 11-01-2019, 04:07 PM   #2
snow_bound26
Scooby Specialist
 
Member#: 395793
Join Date: Jul 2014
Chapter/Region: Tri-State
Vehicle:
2005 92x Aero
Blue

Default

Did you reset the computer after installing the new MAF? Do you mean Prosport? Not passport. Might need to recalibrate the O2 sensor for it or replace it if it's old.

As for the misfire. Have you checked your plugs and coils? Not that all 4 typically go at once. Crank position sensor can cause misfire codes. And lightened flywheels are notorious for it. Especially if they are combined with a light crank pulley.
snow_bound26 is offline   Reply With Quote
Old 11-01-2019, 04:18 PM   #3
Easyy
Scooby Newbie
 
Member#: 507940
Join Date: Nov 2019
Chapter/Region: MWSOC
Location: WI
Vehicle:
2002 wrx
white

Default

Quote:
Originally Posted by snow_bound26 View Post
Did you reset the computer after installing the new MAF? Do you mean Prosport? Not passport. Might need to recalibrate the O2 sensor for it or replace it if it's old.

As for the misfire. Have you checked your plugs and coils? Not that all 4 typically go at once. Crank position sensor can cause misfire codes. And lightened flywheels are notorious for it. Especially if they are combined with a light crank pulley.
No, I didn't know resetting it was a thing lol. I usually drive an obd1 car so im used to dumb ecus lol. I will go try this now. And yeah, could be prosport, I'm just trying to recall it off the top of my head.

And the misfire, I'm pretty sure that its caused by the lean idle, its very lopey and rough at idle but instantly smooths out once driving.
Easyy is offline   Reply With Quote
Old 11-01-2019, 04:35 PM   #4
NicMonte
Scooby Newbie
 
Member#: 479655
Join Date: Dec 2017
Location: Omaha Ne
Vehicle:
2002 Impreza wrx
Black

Default

Quote:
Originally Posted by Easyy View Post
No, I didn't know resetting it was a thing lol. I usually drive an obd1 car so im used to dumb ecus lol. I will go try this now. And yeah, could be prosport, I'm just trying to recall it off the top of my head.



And the misfire, I'm pretty sure that its caused by the lean idle, its very lopey and rough at idle but instantly smooths out once driving.


After my Jdm swap on an 02wrx I had very similar issues.

I replaced front o2, maf. Fuel filter.(none worked)

Replaced injectors and fuel pressure regulator. This fixed the issue. I had the same symptoms. Also I would check your IACV this might be the issue for the looping idle(possibly).
Although, a boost leak could create similar symptoms.
Hope this helps
NicMonte is offline   Reply With Quote
Old 11-01-2019, 04:51 PM   #5
Easyy
Scooby Newbie
 
Member#: 507940
Join Date: Nov 2019
Chapter/Region: MWSOC
Location: WI
Vehicle:
2002 wrx
white

Default

Just went and reset the ECU and went for a spirited drive. No dice, still idles lean. And yes it is a "prosport" afr, my bad lol.

Quote:
Originally Posted by NicMonte View Post
After my Jdm swap on an 02wrx I had very similar issues.

I replaced front o2, maf. Fuel filter.(none worked)

Replaced injectors and fuel pressure regulator. This fixed the issue. I had the same symptoms. Also I would check your IACV this might be the issue for the looping idle(possibly).
Although, a boost leak could create similar symptoms.
Hope this helps
I checked the IACV already, thing looks brand new. Ill look in to the fuel pressure regulator.
Easyy is offline   Reply With Quote
Old 11-01-2019, 08:25 PM   #6
NicMonte
Scooby Newbie
 
Member#: 479655
Join Date: Dec 2017
Location: Omaha Ne
Vehicle:
2002 Impreza wrx
Black

Default

Quote:
Originally Posted by Easyy View Post
Just went and reset the ECU and went for a spirited drive. No dice, still idles lean. And yes it is a "prosport" afr, my bad lol.



I checked the IACV already, thing looks brand new. Ill look in to the fuel pressure regulator.


Also whatís weird is when you unplugged your maf your car ran still...? When I did that my car turned off immediately. Which ruled out the maf in my case. But replaced anyways. My AFRs were loopy, jumping from low 13s to high 15s and occasional 17ish. When the FPR was replaced it fixed the idle AFRs. My injectors were a culprit of high af learning values and long cranks.

Look into why your car would still run with MAF unplugged. And go from there.(if Iím reading your post correctly)? Iím not familiar with Prosport? Is that a afr gauge?
NicMonte is offline   Reply With Quote
Old 11-01-2019, 08:55 PM   #7
Easyy
Scooby Newbie
 
Member#: 507940
Join Date: Nov 2019
Chapter/Region: MWSOC
Location: WI
Vehicle:
2002 wrx
white

Default

Quote:
Originally Posted by NicMonte View Post
Also whatís weird is when you unplugged your maf your car ran still...? When I did that my car turned off immediately. Which ruled out the maf in my case. But replaced anyways. My AFRs were loopy, jumping from low 13s to high 15s and occasional 17ish. When the FPR was replaced it fixed the idle AFRs. My injectors were a culprit of high af learning values and long cranks.

Look into why your car would still run with MAF unplugged. And go from there.(if Iím reading your post correctly)? Iím not familiar with Prosport? Is that a afr gauge?
In most cars when you unplug your maf the ecu goes in to a default mode and corrects fueling by only data from the o2 sensors (at least from what I understand). This is why I thought my maf was bad, but I cleaned my old one and got a new one and it still idles at 17 afr.

And yeah, prosport is a brand of afr gauge. It reads constant 17 afr and the car sounds cammed/lopey at idle and shakes a lot. The second I start moving its fine and the afrs are what id suspect to be normal.

Car doesn't take long to crank, you turn the key and it starts right up.
Easyy is offline   Reply With Quote
Old 11-07-2019, 11:11 AM   #8
subaru_gc8
Scooby Specialist
 
Member#: 29292
Join Date: Nov 2002
Chapter/Region: SCIC
Location: Orange County CA
Vehicle:
2004 WRX wagon
silver

Default

so what you want to do is unmarriy the cobb and see what your afrs are on the gauge, I had a prosport afr and that thing was a pos. I dont know what it is about their gauge but it always read differently, cant remeber if it was high or low but it was one or the other. So yeah honestly I dont think the car would run on a 17:1 afr to be honest.
subaru_gc8 is offline   Reply With Quote
Old 11-07-2019, 03:10 PM   #9
Fozymandias
Scooby Newbie
 
Member#: 504375
Join Date: Jul 2019
Default

Unplug your O2 sensor - if the issue goes away thatís your problem
Fozymandias 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 01:39 PM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2019 Axivo Inc.
Copyright ©1999 - 2019, North American Subaru Impreza Owners Club, Inc.

As an Amazon Associate I earn from qualifying purchases.