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  • #31
    Now you've got it to a stage where it's not cutting out, but also not boosting, I'd try unplugging the MFTS again to see if that makes a difference.
    sigpic
    1991 Audi S2 3B - 2.5 Stroker engine
    1997 A6 2.5TDi quattro avant - C4
    1976 RD250E / 350LC cafe racer

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    • #32
      Originally posted by AndyP View Post
      Now you've got it to a stage where it's not cutting out, but also not boosting, I'd try unplugging the MFTS again to see if that makes a difference.
      We have boost. I don't know how much yet, but it is definitely better with the MFTS unplugged.

      Still got the other two codes

      00281 Road speed signal

      00528 Altitude sensor

      and now

      00515 Hall Sender, but the car starts fine.

      What is the best make of MFTS and where to get it from?
      Steve

      1990 RR 20V
      1982 SWB UR - RS2 Engine

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      • #33
        Have a look at the ECU plug to make sure you don’t have a pin pushed back.

        There’s a thread somewhere about the MFTS, I think the Behr one is good but sure someone will confirm.

        S2 Coupe 3B Project


        Ur quattro restoration

        S2 Avant

        Boost is the new rock and roll!
        sigpic

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        • #34
          Do yuo have a boost gauge you can use to check it? I'm guessing these chips should be 1.8/1.9bar and in such a lightweight car it should be a real handful!!

          Bring it round tomorrow if you need to borrow a guage
          sigpic
          1991 Audi S2 3B - 2.5 Stroker engine
          1997 A6 2.5TDi quattro avant - C4
          1976 RD250E / 350LC cafe racer

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          • #35
            I'll measure the boost in the morning, but it is nowhere near it should be, I'm going to swap the altitude sensor from the RR as well and see if that makes a difference.
            Steve

            1990 RR 20V
            1982 SWB UR - RS2 Engine

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            • #36
              As this is a very early UR (1982) it actually has a built in boost gauge on the dash display but it wasn't working. After tracing the piping through into the engine bay I found where it was disconnected and remade the connection.

              Before going out, the codes were cleared and the altitude sensor fitted from the RR. Interestingly it read 0.69K Ohms whereas mine was 1.03K Ohms. With the MFTS disconnected it achieved around 1.8 to 2 bar according to the dial. In the higher gears, 4th and 5th, the performance was not as quick with the boost considerably less. I didn't spend too long out as I didn't want to melt the engine.

              When I got back I have the same three codes still:

              00281 Road Speed Signal
              00528 Altitude Sensor
              00515 Hall Sender

              The next step for me is to change the MFTS.
              Steve

              1990 RR 20V
              1982 SWB UR - RS2 Engine

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              • #37
                MFTS changed with a BEHR unit and switch reconnected. The car is now boosting with the needle on the boost gauge going right to the top which is identified as 2 bar.

                The car seems to pull pretty well in 1st and 2nd. The boost drops off noticeably after 4500-5000 rpm in 4th and 5th.

                Anyone got any other ideas before I work my way through the above list?
                Steve

                1990 RR 20V
                1982 SWB UR - RS2 Engine

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                • #38
                  Are you using the RS2 loom? There is some suggestion that the altitude sender signal is fed to a trailer recognition relay which would ordinarily be populated by a relay or a jumper. If either are missing that would mean no signal back to the ecu. That could be verified by measuring the signal back at the ecu pin 9. This relay also has the ability to reduce engine boost if it recognises a trailer is connected. I believe it drops boost back to stock ABY levels. So they are a few interconnected possibilities there alone.
                  To be honest you could do with having access to a more precise/accurate boost gauge and vagcom/VCDS. It would be useful to see what the altitude sensor values are from the ecu perspective.
                  The speed sensor issue will not be resolved without actually feeding the ecu with a signal! This could be done externally as is done on more modern Audi's or possibily internally via the speedo IF it has an impulse rotor like certain VAG speedo of similiar vintage. That would possibily need some electronics to get the right signal cycle. Again there is a suggestion that there will be a rpm limiter if the signal fails although it is above 5K rpm.
                  Lastly have you checked the cambelt timing? Not sure what combo of flywheel gearbox you are using but the hall sensor code might be an indication that the timing is out which is important on the ADU as the correct timing is half a tooth out rather than a straight forward alignment of the marks.. Would be useful to verify that whatever TDC mark is used is an accurate one.

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                  • #39
                    Yes, I am using the RS2 loom. I do have a better boost gauge and will get it connected. Any advice where I can get a copy of the Vagcom/VCDS is appreciated.

                    I had actually been reading about the timing the day before your post. Having a few minutes spare this evening I took the covers off and found the following:

                    1. Timing mark on the Crank Pulley lines up with the oil pump.
                    2. The '0' on the Flywheel also looks right.
                    3. Crankshaft Pulley looks wrong.



                    Last edited by steverrquattro; Yesterday, 20:12.
                    Steve

                    1990 RR 20V
                    1982 SWB UR - RS2 Engine

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                    • #40
                      Looks out as it as the line should be to the left of the v on the cover. There are some better pics.
                      If you are using the matching flywheel/gearbox then that should be a more accurate determination than the pulley.
                      Trying to get that 0 aligned is a PITA as its difficult to see whether its splitting it or not.

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                      • #41
                        https://www.s2forum.com/forum/techni...60#post2001960

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                        • #42
                          Another thought. I would inspect the cambelt carefully in case its not the correct 150 tooth belt. If you are lucky and the belt is reasonably fresh (unlikely) perhaps it still has a part number on it. Wouldn't hurt to check the waterpump is RS2 as well. Campulley seems to be correct so there's some good news!

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