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MAF Problem?

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  • MAF Problem?

    Unfortunately I only have the Haynes manual for my Mk4 Bora. I have had higher than average fuel consumption and some black exhaust smoke when hot. This is not all the time. Sometimes it runs ok but then others it chews through the fuel. My shareware vag shows faults in the MAF and the Lambda sensor.
    The manual is next to useless for the petrol engine emissions but in the diesel section, it says there is supposed to be 12 volts between terminal 2 and 3 of the MAF connector and around 5 volts between terminals 3 and 4. I have the 5 volts but nothing between terminals 2 and 3. Both terminal 2 and 3 seem to be earths as the multimeter shows battery voltage when connected between each terminal individually and the battery.
    Any suggestions?

    Thanks in advance

    doc
    Last edited by doc; 28-10-2009, 01:59 PM.

  • #2
    Have no idea about the voltage stuff sorry.

    How many Km on your car, what year? has it had any other sensors etc changed in the past?

    Can show up as being MAF on checkers but from my past experience it may not always be.

    Have you tried disconnecting the battery to reset the ecu? Also hows the temperature gauge after 5-10mins of the motor running?
    Bora gone
    Vento VR6
    MKIV GSW TDI
    7P Touareg TDI

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    • #3
      What engine doc?

      Coolant temp sensor and Lambda more likely to cause symptoms in my experience.

      If you can't get a better scan from the ECU with another VAG-COM. The temp sensor is a cheaper speculative replacement.

      Gavin
      optimumcode@gmail.com | https://www.vwwatercooled.com.au/for...i-;-79012.html | https://www.facebook.com/TTY-Euro-107982291992533

      Comment


      • #4
        It's the 2 litre with an auto. I replaced the coolant sensor about 4 months ago. It does seem to show a bit low at times.
        The car has 113000k's and I'm not sure whether any other sensors have been changed in the past.
        I have disconnected the battery for a while to reset the ecu but it didn't seem to make a difference.
        I got a new catalytic converter 2 days ago as the old one was rattling. I saw inside the old one and it was starting to block up. It does seem to be using less fuel since then and I haven't seen any smoke but it could be my imagination. Maybe I should just take it to the local vw place for a proper scan.
        Thanks for the replies.
        Last edited by doc; 29-10-2009, 04:11 AM.

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        • #5
          Thermostat is stuck open then mate, this will have the same characteristic of a failing temp sensor, engine will run cool and the injection pulse width will then be longer thus more fuel consumption, changed heaps of stats on these mate. What is the heater like on hot mate , is it like an oven or luke warm that will geive you a good idea too
          Cheers
          Jmac
          Alba European
          Service, Diagnostics and repairs. Mobile Diag available on request
          Audi/VW/Porsche Factory trained tech 25+ yrs exp
          For people who value experience call 0423965341

          Comment


          • #6
            Originally posted by doc View Post
            Unfortunately I only have the Haynes manual for my Mk4 Bora. I have had higher than average fuel consumption and some black exhaust smoke when hot. This is not all the time. Sometimes it runs ok but then others it chews through the fuel. My shareware vag shows faults in the MAF and the Lambda sensor.
            The manual is next to useless for the petrol engine emissions but in the diesel section, it says there is supposed to be 12 volts between terminal 2 and 3 of the MAF connector and around 5 volts between terminals 3 and 4. I have the 5 volts but nothing between terminals 2 and 3. Both terminal 2 and 3 seem to be earths as the multimeter shows battery voltage when connected between each terminal individually and the battery.
            Any suggestions?

            Thanks in advance

            doc
            Look in my post in here how to test MAF
            Let us know how did you go.
            Performance Tunes from $850
            Wrecking RS OCTAVIA 2 Link

            Comment


            • #7
              Thanks for the replies. It came good for a few days so I thought it may have been a bad connection. (I checked all connections and jiggled them)

              Jmac
              I was thinking the thermostat may be playing up as as times it takes a while to warm up and the heater is not at hot as it used to be. I didn't think that would effect the ECU as my last car was a 1976 Holden Ute. The closest to a computer in that was electronic ignition.

              Transporter

              I followed your test as best I could as remembering I only have the Vagcom shareware. It logged
              P1570
              P1544
              P0134
              P1128
              P0171
              P0102
              It turns out I do actually have 12 volts at the MAF and everything else appears to be OK.

              I VCDS under group 03 I didn't have mg/stroke. The closest was g/ms or similar. That was about 5.2 if that means anything. I can't take it for a drive as I don't have a laptop. Only a hardwired jobby

              The problem is when it's at operating temperature but I'll try a thermostat first and see how it goes. If not, down to Volkwerke for a scan and some work.

              doc

              Comment


              • #8
                Yeah it affect the running condition, doesnt upset the computer as such its merely doing what its told, engine is cooler so the injection pulse is wider thus lots richer, done a few now, so really when the stat is playing up and the engine is cool its doing what a faulty temp sensor would do ( tell the ecu the engine is cold) if you catch my drift.
                See how you go. Fit it, bleed it and clear all your faults and go for a blast, whilst you are there check all induction system is in good order, vac lines or splits.
                Good luck
                Jmac
                Alba European
                Service, Diagnostics and repairs. Mobile Diag available on request
                Audi/VW/Porsche Factory trained tech 25+ yrs exp
                For people who value experience call 0423965341

                Comment


                • #9
                  Rev the engine and the MAF output will change. Drivng it would be a better test though.

                  Gavin
                  optimumcode@gmail.com | https://www.vwwatercooled.com.au/for...i-;-79012.html | https://www.facebook.com/TTY-Euro-107982291992533

                  Comment


                  • #10
                    I have to check the rest of the OBD2 codes but I know for sure that P0171 is lean mixture and P0102 is MAF low output.
                    Can you log the data in VCDS?
                    You should also check your oxygen sensor.
                    Last edited by Transporter; 02-11-2009, 06:08 PM. Reason: add link
                    Performance Tunes from $850
                    Wrecking RS OCTAVIA 2 Link

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                    • #11
                      Ok if you check your O2 sensor and the stat is stuck open it will be reading rich along with a longer duty cycle on the injectors, all checkable with measured blocks on Vagcom. If you still query the o2 sensor pull the vac line off the fuel pressure reg then itll richen, blanking off the vac at the same time. Now check it for lean switching, create an air leak. All very checkable with Vagcom. You mention the fact its at op temp well the system is on closed loop then.
                      good luck with tests
                      Jmac
                      Alba European
                      Service, Diagnostics and repairs. Mobile Diag available on request
                      Audi/VW/Porsche Factory trained tech 25+ yrs exp
                      For people who value experience call 0423965341

                      Comment


                      • #12
                        Originally posted by Jmac View Post
                        Ok if you check your O2 sensor and the stat is stuck open it will be reading rich along with a longer duty cycle on the injectors, all checkable with measured blocks on Vagcom. If you still query the o2 sensor pull the vac line off the fuel pressure reg then itll richen, blanking off the vac at the same time. Now check it for lean switching, create an air leak. All very checkable with Vagcom. You mention the fact its at op temp well the system is on closed loop then.
                        good luck with tests
                        Jmac
                        Hey there, Jmac.
                        All we need now is his car.
                        Performance Tunes from $850
                        Wrecking RS OCTAVIA 2 Link

                        Comment


                        • #13
                          Originally posted by Transporter View Post
                          Hey there, Jmac.
                          All we need now is his car.
                          Haha true story mate
                          cheers
                          Jmac
                          Alba European
                          Service, Diagnostics and repairs. Mobile Diag available on request
                          Audi/VW/Porsche Factory trained tech 25+ yrs exp
                          For people who value experience call 0423965341

                          Comment

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