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    Thread: P0170 Fuel Trim Malfunction Bank 1 on '01 GTI

    1. Member
      Join Date
      Jun 8th, 1999
      Location
      Boston, MA
      Posts
      1,083
      Vehicles
      2010 GTI 2.0T 6spd, 2001 GTI 1.8T 5spd
      06-03-2010 03:06 PM #1
      I have this error code on my '01 GTI. I have searched for vacuum leaks. I just replaced the MAF and cleaned the throttle body. I still get this code intermittently every 3 weeks or so. Any ideas?
      Last edited by olaf; 06-05-2010 at 07:40 PM.
      01 GTI 1.8T 195k
      06 Chevy Colorado 4x4 5spd 75k
      10 GTI 2.0T 6spd 60k

    2. 06-03-2010 04:45 PM #2
      what does your block 032 read? are you misfiring and getting backfires?
      MK4 Junker : PAG 50trim Kit : AEB : RMR : Eurodyne
      P.P.T. - Pag Parts Turbo
      B6 A4 : Slow

    3. Member
      Join Date
      Jun 8th, 1999
      Location
      Boston, MA
      Posts
      1,083
      Vehicles
      2010 GTI 2.0T 6spd, 2001 GTI 1.8T 5spd
      06-05-2010 10:13 AM #3
      The car runs quite good. What seems to happen is that every few weeks the car momentarily loses power, the CE comes on, and then everything goes back to normal.

      I am replacing the 3-way crankcase ventilation hose today. It is practically collapsing. I wonder if that could cause the problem? I am also going to clean the pancake valve while I am in there. I will check the readings on block 032 and report back.
      01 GTI 1.8T 195k
      06 Chevy Colorado 4x4 5spd 75k
      10 GTI 2.0T 6spd 60k

    4. Member
      Join Date
      Jun 8th, 1999
      Location
      Boston, MA
      Posts
      1,083
      Vehicles
      2010 GTI 2.0T 6spd, 2001 GTI 1.8T 5spd
      06-05-2010 02:02 PM #4
      Okay I replaced the hose and cleared the codes. I checked Block 032 and I am reading 0% in both fields. Hummm. I am not sure if the problem is fixed, but I will monitor and check back later if I get an error code.
      01 GTI 1.8T 195k
      06 Chevy Colorado 4x4 5spd 75k
      10 GTI 2.0T 6spd 60k

    5. 06-05-2010 02:06 PM #5
      When you clear codes you reset your adaptation. You just blew up your old fuel trim values by doing that. drive it for a week and report back. I believe half of '01s have a wideband primary O2 sensor, assuming you are wideband when's the last time you had that sensor changed?
      MK4 Junker : PAG 50trim Kit : AEB : RMR : Eurodyne
      P.P.T. - Pag Parts Turbo
      B6 A4 : Slow

    6. Member
      Join Date
      Jun 8th, 1999
      Location
      Boston, MA
      Posts
      1,083
      Vehicles
      2010 GTI 2.0T 6spd, 2001 GTI 1.8T 5spd
      06-05-2010 05:27 PM #6
      I recently purchased the car, but the cat and 02 were replaced last year.

      Now I am getting a 17705 - Pressure Drop between Turbo and Throttle Valve (check D.V.!)
      P1297 - 35-00 - -

      It hasn't yet tripped the CE, but it stores the code. I think I still have a bad hose somewhere. The lower crankcase breather hose (the weird plastic one) feels real mushy.

      Here is what I have done so far:

      new coil packs (5 months ago)
      new coil overlay harness (5 months ago)
      new MAF
      cleaned TB (both mechanical & electrical) & ran adaption
      replaced upper 3-way valve cover hose
      cleaned pancake valve (it looked fine)
      inspected diverter valve (but i suppose it could be bad)

      The car seems to operate fine, so this has got to be just a stupid vacuum leak somewhere, no?
      Last edited by olaf; 06-05-2010 at 07:41 PM.
      01 GTI 1.8T 195k
      06 Chevy Colorado 4x4 5spd 75k
      10 GTI 2.0T 6spd 60k

    7. Member
      Join Date
      Jun 8th, 1999
      Location
      Boston, MA
      Posts
      1,083
      Vehicles
      2010 GTI 2.0T 6spd, 2001 GTI 1.8T 5spd
      06-12-2010 03:24 PM #7
      Update:

      After replacing both the upper valve cover breather hose and the lower plastic breather hose, I was still having the 17705 pressure drop problem. So I replaced my MAF with my original MAF and re-aligned the throttle body. Now I am not getting any error codes. I think the replacement MAF was bad.

      I have checked all sorts of values. My MAF idles in the proper range of 2-4 and will go up to like 100+ when under full acceleration. So I think it is okay.

      As for the fuel trims, before I realigned I was at 1.3% and -3.1%.

      I logged misfires and I get none. Occasionally, like once every 10 minutes of driving I will see one misfire on a cyclinder, but then it goes away. Sometimes I see none. Is this normal?

      I guess I am just going to drive for a bit and see what else trips. Really weird.
      01 GTI 1.8T 195k
      06 Chevy Colorado 4x4 5spd 75k
      10 GTI 2.0T 6spd 60k

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