Jump to content

Welcome to RennTech.org Community, Guest

There are many great features available to you once you register at RennTech.org
You are free to view posts here, but you must log in to reply to existing posts, or to start your own new topic. Like most online communities, there are costs involved to maintain a site like this - so we encourage our members to donate. All donations go to the costs operating and maintaining this site. We prefer that guests take part in our community and we offer a lot in return to those willing to join our corner of the Porsche world. This site is 99 percent member supported (less than 1 percent comes from advertising) - so please consider an annual donation to keep this site running.

Here are some of the features available - once you register at RennTech.org

  • View Classified Ads
  • DIY Tutorials
  • Porsche TSB Listings (limited)
  • VIN Decoder
  • Special Offers
  • OBD II P-Codes
  • Paint Codes
  • Registry
  • Videos System
  • View Reviews
  • and get rid of this welcome message

It takes just a few minutes to register, and it's FREE

Contributing Members also get these additional benefits:
(you become a Contributing Member by donating money to the operation of this site)

  • No ads - advertisements are removed
  • Access the Contributors Only Forum
  • Contributing Members Only Downloads
  • Send attachments with PMs
  • All image/file storage limits are substantially increased for all Contributing Members
  • Option Codes Lookup
  • VIN Option Lookups (limited)

Recommended Posts

Hi All

 

My first post here so please bear with me but pretty desperate for help.  Have 2004 Boxster S and its, in general, running a bit rough (feels fuel rich).  It also will also, on occasion, not go.   Pulling up at a busy intersection and car reduces to Idle.  Then put the foot down and the car stays at idle.   Normally an engine restart gets things going again (although not always and sometimes requires a few goes).  

 

Bought a computer reader and found error codes

P0102:  Factory Fault code 115 - Mass air flow sensor - below limit

P2135: Accelerator Pedal - Signal Implausible

P0121: Factor Fault code 117 - Throttle value or accelerator pedal potentiometer - signal implausible

P1266: Factory Fault Code 409 - Fuel shutoff function monitor - signal implausible

 

Took the car to Porsche.  They suggest a MAF sensor was the root cause and replaced it.   It felt better for a few days then problem returned.  They replaced another MAF sensor.. Same problem.   They then said the MAF reads 0 and have checked the cables so its me DME and it needs replacing (not cheap)

 

Have taken the car back home and looked at the likely affecting values myself from the computer.

 

1. MAF

The computer shows to different values for MAF

Mass air flow (HFM) is always 0 regardless of if the car is working correctly or not and at any accelerator level 

Mass air flow seems to move within a range of 18 (idle) to 100 (full throttle)

 

2. Throttle  (since it had error codes on this)

Pedal encoder potentiometer 1 and 2 always move and the pedal value goes from 0-100% when its working but stays at 0 when its not.  Since the potentiometers always move I am assuming the DME simply can't add things up so sticks the pedal value at 0.

 

ie.   The MAF sensor reading above confuses the DME and it reduces the throttle to 0.  That feel consistent with the behaviour of the car (its just sticks at idle)   

 

Any one with any clues?  Certainly don't want to replace the DME unless absolutely necessary....

 

HELP?

 

 

 

 

 

 

Share this post


Link to post
Share on other sites

:welcomeani:

 

I would hope they took the time to clean the electrical connections on the both the throttle valve positioner and the accelerator pedal electrical connector.

Using their PIWIS tester they can check to see if the throttle butterfly is opening all the way when you press the accelerator pedal - if it does not then the e-gas throttle valve positioner or the accelerator pedal sensor is not working to send the signal.

 

I would expect an MAF fault if the throttle butterfly was not opening.

Share this post


Link to post
Share on other sites

Thanks Loren... Might be a lot to assume anything from Porsche service so will check those myself on the weekend.   The "raw value" from my super cheap computer reader from the accelerator potentiometers does change so seems unlikely to be that. i have attached the values and you can see the "Mass air flow (HFM)" is stuck at 0.    It never moves.  The other "Mass air flow" value seems to move in what would be expected with increasing RPM and has a value when at idle of about 18".   Hence i suspect its related to this (see attached)

 

When i had the computer plugged it i didn't see the throttle values changing but didn't record them.  I will rerun that over the weekend to see if its working roughly as i would expect.

values.tiff

Share this post


Link to post
Share on other sites

Looks like the culprit may be the pedal position sensor. The reading of potentiometer 1 needs to be exactly double that of pot 2.

With key ON engine OFF, monitor these two numbers while you press on the gas pedal slowly for the whole range of motion of the pedal, then repeat a few times. Look carefully for spots where these two numbers are not 1:2

Share this post


Link to post
Share on other sites

Thanks Ahsai... I took the readings and at no time is POT 1 double POT 2.   I have attached idle, full and somewhere in-between readings (see attached).   Also, the POT 2 value moves.  Its never static, even at idle (at idle it moves between 0.47 and 1.0 while POT 1 is static at 0.78V).    Would that be enough to suspect and replace the accelerator pedal?

 

There were two mass airflow readings as well

 "Mass air flow (HFM)" is stuck at 0 - always.

"Mass air flow" moves with engine RMP

 

I was headed in that direction until you mentioned the accelerator pedal

Full

full.png

 

Half

half.png

 

Idle

idle.png

 

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Similar Content

    • By Angel Martin
      I need to replace the ATF wiring harness in my 2002 986 w/ tiptronic due to a defective temperature sensor that forms part of it. I have been unable to find any information as to what it entails and / or how it can be replaced.   Appreciate any insight. 
    • By nightrn1
      I'm new to the Porsche family.... Just over a month and the proud owner of a 1999 Boxster.  It's a project car but still on the road and my point to point ride.  Must say, LOVE to drive this car....This one has  been lowered some, well alot... and does it hug the road..... Just doesn't miss much being that low....  My question is, I am having an issue with the rear lights on this car...  I know I had a problem with the left rear brake light.  I tried tracing back the wire but found no problem... I then switched the lamp holder from the right side to the left and all the lights worked... So I thought I had an equipment issue.  I bought a (Porsche) replacement bulb holder.  Came in last night.  Changed out today...Guess what????  Turn indicators work, Backup lights work,  Brake light works on the Right Side ONLY, (still) Now no rear tail lights what so ever......I have checked ALL the fuses, only had to replace one and it had nothing to do with the lights.  NOTHING has changed....Where did my tail lights go??????  Can't figure this out.......Please help.......Just FYI,  ALL the LIGHTS were working as of last Wed. when I did the bulb holder swap and checking the lights.  Power is to both wire harnesses.   Everything else works except the left brake light and the drive lights.  Go figure.......
    • By mrplow911
      The radiator grills on the 986 sit very low and thus tend to collect quite a bit of debris and garbage faster than other cars.  The design of the radiators and front air intakes is such a way that any debris which enters the grill get jammed between the radiator and the inside of the front bumper body panel.  
      Cleaning out your radiators and the garbage stuck behind the front bumper should be done periodically as leaving anything in there can cause inefficiencies to your cooling (A/C and engine) and also rust your radiators once the debris gets wet.  
      By adding mesh to the standard grill, using gutter guards for rain gutters, you can reduce the amount of debris which can enter your grill.  This is a simple process and adds not only functional value, but I think it looks pretty great too.  For me it took roughly 4 hours to access, clean the radiators and air intakes, and add the mesh to my front grills(not including painting the grills).
      Parts you'll need:
      •    Gutter Guard (this is the same stuff you use for rain gutters on a house to keep leaves and junk from building up in the gutter) - Buy two sheets of this.
      •    High gloss, black spray paint
      •    Tiny black zip ties - nothing too thick, but don't go too wimpy either.  You'll need about 4 zip ties.
      Tools you'll need:
      •    Torx set
      •    Vacuum
      •    Aluminum shears
      •    Wet rag and soap to wipe down the air intake duct which is likely dirty.
      I won't cover how to remove the front bumper, as that's available widely across Youtube, Renntech, and other DIY sites.  Here's the Youtube video I used (https://www.youtube.com/watch?time_continue=280&v=X2q54XtupVo).  
      So we'll get started with this tutorial once you have the front bumper cover removed.

      1.    The first step is to remove the grills which are held in place with 4 plastic tabs and pull out from the inside of the front bumper cover.  This is fairly straight forward – just be sure to follow the general rule of not trying to force anything!  Use the images below to help.


       
      From this image, you can see 4 plastic tabs are used to secure the grill in place, while 3 tabs on top are flat and just used to align the grill.
      2.    With the grills out, it’s time to trace them on paper so you can cut your mesh correctly.  I used a big sheet of painters drop paper, which I’ll later use when painting the grills, to trace around the whole perimeter of the grill piece.  It’s important to trace around the whole piece rather than just the vent portion, because the grill is rounded and so the mesh will need to bend in order to make this a tight fit.  If your mesh is too small debris will be able to make it past your grill.
      3.     Now it’s time to cut your gutter guard.  Using the metal shears, cut the mesh to match the outline you traced in step 2.  I found it easy to use a box knife to score and transfer the tracing from the paper to the gutter guard (since the gutter is painted, you just use the box knife to score the paint).

      Your cuts don’t need to be perfect.  Mine aren’t rounded, but you’ll see that they still create a great seal for stopping junk.
      4.    This next step is optional, though it makes a big difference in terms of looks!  I painted by grills.  There’s nothing fancy you need to do when painting them.  I applied three coats of paint just to ensure it was solid.  Let them dry for at least a day or two or else the paint will easily chip.   
      5.    The next step is to cut a whole out for the outside temp sensor which is sticks through the left grill (when looking at the car head on).  Before cutting the hole for the sensor, be sure to test out your mesh by holding it against and fitting it (bending it to form) with the respective grill it’s for.  
       This doesn’t need to be an exact science, and in this case it’s always better to cut less and test it rather than cut too much.
      I determined where the hole needed to be cut by holding the fitted mesh against the grill and scoring the part of the mesh which aligned with the hole on the grill.  I cut a small rectangle that is about a half inch, or in my case three snips of the mesh.  I probably couldn’t gone a bit smaller, but you can’t really notice. 
       

      6.    Next step is to adhere the mesh to the grill.  I did this a bit differently than others have since I didn’t’ want the mesh to be permanently attached to the grill.  I used small black zip ties which aren’t visible when viewing the car but hold the mesh securely in place and allow it to be replaced if they become damaged or a future owner doesn’t want them.  In the picture below you can see I used 4 zip ties for each grill.  Two on the very bottom which help support the mesh from sliding down, and two at the very top which help the mesh from being pushed back into the intake duct. 

      7.    The most difficult part of reassembly is aligning the outside temp sensor with the hole you made.  Prior to having mesh installed this was simple because you could just put your fingers in the grill and guide it.  There’s no trick to this, just take your time aligning it as you put the bumper panel back on.  It doesn’t need to be aligned perfectly since you can use needle nose pliers to adjust it after the bumper panel is in place. 
    • By mrplow911
      View this tutorial Radiator Grill Mesh and Painting
      The radiator grills on the 986 sit very low and thus tend to collect quite a bit of debris and garbage faster than other cars.  The design of the radiators and front air intakes is such a way that any debris which enters the grill get jammed between the radiator and the inside of the front bumper body panel.   Cleaning out your radiators and the garbage stuck behind the front bumper should be done periodically as leaving anything in there can cause inefficiencies to your cooling (A/C and engin Author mrplow911 Category Boxster (986) - Mods Submitted 03/23/2019 06:59 AM Updated 03/23/2019 07:46 AM  
    • By Christiaan Poortman
      Hello, I'm new on this forum and stumbled upon a new problem (or old) with my 2.5l 986 Boxster from 1997.
       
      The problem occurs when the engine is started dead cold after sitting a few hours/overnight.
       
      Engine starts immediately but the RPMs start to surge / hunt between 1100 and 700 RPM. This continues for about 10 seconds after which the idle smoothes out to the normal cold idle RPM. 
       
      The first pull away requires a tad more throttle then normal to prevent stalling. After this first pull, everything is almost normal and engine performance becomes better and better. When the engine is hot, the idle sits at 780 RPM with a minor fluctuation now and then (seems to be more than normal)
       
      I've been to two shops (official Porsche dealer and local Porsche specialist). Porsche dealer couldn't find anything and the specialist found the camshaft sensor on the left bank to be unplugged - but now comes the strange thing - the cabling is nowhere to be found!!!!!!? Took the car home to check myself but didn't find anything.
       
      No camshaft related codes to be found in the diagnosis and no CEL either. 
       
      Attached one pic showing the sensor and it's missing plug
       
      Could someone help me out? - Is it possible for the engine not to throw a CEL when sensor is disconnected? - where is the sensor wire to be found?

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.