P0171 & Power Erratic
Results 1 to 11 of 11

This is a discussion on P0171 & Power Erratic within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; Hoping to get some expert advice here if you all would be so kind. Here's all the information. My baby, ...

  1. #1
    Registered User
    Join Date
    Nov 2006
    Posts
    11

    Unhappy P0171 & Power Erratic

    Hoping to get some expert advice here if you all would be so kind. Here's all the information. My baby, which I love, is sick, 2002 WRX sedan, 55000 miles, everything stock never modded, and it's out of warranty since August.

    Problems began October 27th, MIL came on with a DTC of P0171 (System Too Lean). Power was questionable (hesitation/erratic) under hard acceleration in any gear, particularly in a spot between 4000-4500 rpm. Opening the throttle up in a higher gear (say 4th) seemed to be the trigger that caused the ECU to report the P0171. MIL came on several times with P0171 and I cleared it several times. Couple of those times the EVAP monitor was set to incomplete as well.

    I tried a couple of light maintenance remedies. Replaced the Air Filter because the old one was pretty dirty. Checked the MAF sensor for dirt, found it to be clean. Put a bottle of fuel injector cleaner in a fresh tank of gas. These things probably retrieved some lost power but didn't resolve the symptoms.

    November 6th I took it into the dealership for diagnosis. The mechanic there took the snapshot out of the OBD, checked all the solenoids out ok, checked the fuel pressure ok. I asked him to do a vacuum leak test because I suspected a leak somewhere in the intake perhaps downstream of the MAF, but he didn't do this. Instead Subaru told him to replace the bank 1 heated O2 sensor in the downpipe and reflash the ECM to a newer version and reset it. Special ordered the O2 sensor part. Went in yesterday (November 16th) and had it done along with a LOF for good measure.

    Initially power seemed more smooth and the MIL wasn't coming back on, and I was feeling good. But by the end of the night yesterday coming back up the freeway, on goes the MIL, P0171 again, this time with the EVAP and O2 SENSOR monitors set incomplete. And the power is again erratic in the 4000-4500 rpm range. Right where the boost starts to be felt. So I realized I just spent the cash out of pocket for the O2 sensor replacement part and labor, and the problem isn't resolved. #%$&!

    Before I go back and raise hell with the service department at the dealership, I want to find out what you guys think. My inclination is to tell them to do a vacuum leak test like I asked for in the first place. Maybe it's just a loose clamp or cracked air duct somewhere, you know, something less severe. Maybe the turbo is dead, something more severe, I just don't know. TIA
    Last edited by z0ned; 11-17-2006 at 01:58 PM.

  2. Remove Advertisements
    ClubWRX.net
    Advertisements
     

  3. #2
    ODJ
    ODJ is offline
    Registered User ODJ's Avatar
    Join Date
    Jan 2006
    Location
    Tampa, FL
    Posts
    357
    This is just a shot in the dark, but have you ever replaced your fuel filter in 55k miles?
    UNSPOILT BY PROGRESS

  4. #3
    Registered User
    Join Date
    Nov 2006
    Posts
    11
    This is just a shot in the dark, but have you ever replaced your fuel filter in 55k miles?
    Yes the fuel filter would have been replaced at major service at 30,000 mi. Also the mechanic performed a fuel pressure test as part of the diagnosis and got normal results. So I consider the fuel system eliminated as a potential culprit.

  5. #4
    Administrator Trainrex's Avatar
    Join Date
    May 2003
    Posts
    26,591
    I Support ClubWRX
    Quote Originally Posted by z0ned View Post
    Hoping to get some expert advice here if you all would be so kind. Here's all the information. My baby, which I love, is sick, 2002 WRX sedan, 55000 miles, everything stock never modded, and it's out of warranty since August.

    Problems began October 27th, MIL came on with a DTC of P0171 (System Too Lean). Power was questionable (hesitation/erratic) under hard acceleration in any gear, particularly in a spot between 4000-4500 rpm. Opening the throttle up in a higher gear (say 4th) seemed to be the trigger that caused the ECU to report the P0171. MIL came on several times with P0171 and I cleared it several times. Couple of those times the EVAP monitor was set to incomplete as well.

    I tried a couple of light maintenance remedies. Replaced the Air Filter because the old one was pretty dirty. Checked the MAF sensor for dirt, found it to be clean. Put a bottle of fuel injector cleaner in a fresh tank of gas. These things probably retrieved some lost power but didn't resolve the symptoms.

    November 6th I took it into the dealership for diagnosis. The mechanic there took the snapshot out of the OBD, checked all the solenoids out ok, checked the fuel pressure ok. I asked him to do a vacuum leak test because I suspected a leak somewhere in the intake perhaps downstream of the MAF, but he didn't do this. Instead Subaru told him to replace the bank 1 heated O2 sensor in the downpipe and reflash the ECM to a newer version and reset it. Special ordered the O2 sensor part. Went in yesterday (November 16th) and had it done along with a LOF for good measure.

    Initially power seemed more smooth and the MIL wasn't coming back on, and I was feeling good. But by the end of the night yesterday coming back up the freeway, on goes the MIL, P0171 again, this time with the EVAP and O2 SENSOR monitors set incomplete. And the power is again erratic in the 4000-4500 rpm range. Right where the boost starts to be felt. So I realized I just spent the cash out of pocket for the O2 sensor replacement part and labor, and the problem isn't resolved. #%$&!

    Before I go back and raise hell with the service department at the dealership, I want to find out what you guys think. My inclination is to tell them to do a vacuum leak test like I asked for in the first place. Maybe it's just a loose clamp or cracked air duct somewhere, you know, something less severe. Maybe the turbo is dead, something more severe, I just don't know. TIA
    Thank you for the great information.

    I'm leaning towards a boost/vacuum leak. If you want to DIY, check your turbo inlet hose, and the plastic y-pipe under the TMIC. Those are the normal suspects.

  6. #5
    Registered User Damien02WRX's Avatar
    Join Date
    Dec 2005
    Location
    California City, CA
    Posts
    441
    Quote Originally Posted by Trainrex View Post
    Thank you for the great information.

    I'm leaning towards a boost/vacuum leak. If you want to DIY, check your turbo inlet hose, and the plastic y-pipe under the TMIC. Those are the normal suspects.
    +1 on the turbo inlet hose. Mine ripped right were the flexible portion is that clamps to the turbo inlet causing the same code you are experiencing.

  7. #6
    Registered User PolarisSnT's Avatar
    Join Date
    Aug 2002
    Location
    Staten Island, NY
    Posts
    3,864
    Check those out as they are easy to do yourself. If you find something Id go back to the dealer and complain. It may not do anything but its worth a shot considering you told them to do this.

    Thinking about it though, a leak in teh y-pipe would cause a rich problem, not lean. If there is a leak, its pre-turbo after the MAF sensor.
    Dan- 2004 PSM 5spd

    "Days get shorter, nights get longer, snow gets deeper, life gets better."

  8. #7
    Administrator Trainrex's Avatar
    Join Date
    May 2003
    Posts
    26,591
    I Support ClubWRX
    Quote Originally Posted by PolarisSnT View Post
    Check those out as they are easy to do yourself. If you find something Id go back to the dealer and complain. It may not do anything but its worth a shot considering you told them to do this.

    Thinking about it though, a leak in teh y-pipe would cause a rich problem, not lean. If there is a leak, its pre-turbo after the MAF sensor.
    Under boost - rich. Under vacuum - lean.

  9. #8
    Registered User PolarisSnT's Avatar
    Join Date
    Aug 2002
    Location
    Staten Island, NY
    Posts
    3,864
    Quote Originally Posted by Trainrex View Post
    Under boost - rich. Under vacuum - lean.
    I thought of that but hes stating under hard acceleration around 4-4.5k rpms so I assume hed be under boost. Still worth a check though.
    Dan- 2004 PSM 5spd

    "Days get shorter, nights get longer, snow gets deeper, life gets better."

  10. #9
    Administrator Trainrex's Avatar
    Join Date
    May 2003
    Posts
    26,591
    I Support ClubWRX
    Quote Originally Posted by PolarisSnT View Post
    I thought of that but hes stating under hard acceleration around 4-4.5k rpms so I assume hed be under boost. Still worth a check though.
    There are a couple different lines of thinking in this case. A boost leak would cause a stumble during 4-4.5k.

  11. #10
    Registered User
    Join Date
    Nov 2006
    Posts
    11
    Some of you mentioned I could access the turbo inlet hose myself. I've never done any major work on my WRX before, only light maintenance. I'm a total beginner. Can I really attempt this myself? How do I learn how?

    Also, where do I find out the price of a replacement stock turbo inlet hose? I dont see any on subaruparts.com

    BTW the problem persists unresolved, all I have had done since last post was replaced the fuel filter and reset the ECM. Every time the ECM is reset power is smooth for like 12-18 hours then the ECM realizes there is a trim issue and symptoms resume. So a leak in the turbo inlet hose or a related duct is definitely now my prime suspect.

    Thanks! All advice above has been extremely helpful.

  12. #11
    Registered User momo02WRX's Avatar
    Join Date
    Sep 2006
    Location
    SRQ, FL
    Posts
    107
    Here's a link to a tutorial on putting a turbo inlet hose in, you can use it as a starting point for checking it for leaks/cracks.

    http://www.scoobymods.com/forums/sho...ht=turbo+inlet

    If it is the problem, you might as well get an aftermarket silicone one that will perform better. Samco & Perrin are a couple brands that make popular ones. They have some of them on EBay ... or just do a Google search for WRX turbo inlet hose and you should find other places that sell them. I've never seen a price for an OEM turbo inlet hose new, but I doubt its much cheaper.
    02 MBP Stg 2 Bugeye
    Bugeye Mafia #107

    WRB '02 Stage 2+ WRX - SOLD (and dearly missed)

    07 OBP WRX (Wife's) SOLD

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •