Boost Problems, what next? (video)

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  • montez
    S2Forum Addict
    • May 2010
    • 396
    • Country: England

    #46
    I have just tried it and the car was getting 1.5 bar of pressure + but was not getting boost cut, it did feel to stall at one bit between a gear change but the car is boosting properly between gear changes. I am guessing the n75 might be sticking a bit when it cycles, I have one of the heavy duty ones so i can strip it down and see.

    I don't know why it was not boost cutting though?
    1991 Audi S2 Coupe

    Comment

    • S2central.net
      Retired OG Mod
      • Jul 2003
      • 16590
      • Country: Northern Ireland

      #47
      Put a fresh N75 in there... and make 100% sure it is plumbed in correctly
      Paul Nugent
      Webmaster http://S2central.net
      Administrator http://S2forum.com

      1994 S2 Coupe ABY - aka Project Lazarus
      2001 A6 allroad 2.5TDi - family tank
      2003 S4 Avant 4.2 V8 - daily burble

      Purveyor of HomeFries and Exclusive agent for Samco hose kits (S2/RS2)

      There are only 10 kinds of people that understand binary - those that do, and those that don't

      Comment

      • S2central.net
        Retired OG Mod
        • Jul 2003
        • 16590
        • Country: Northern Ireland

        #48
        Also do output tests from ecu to ensure you have electrical connection working to N75
        Paul Nugent
        Webmaster http://S2central.net
        Administrator http://S2forum.com

        1994 S2 Coupe ABY - aka Project Lazarus
        2001 A6 allroad 2.5TDi - family tank
        2003 S4 Avant 4.2 V8 - daily burble

        Purveyor of HomeFries and Exclusive agent for Samco hose kits (S2/RS2)

        There are only 10 kinds of people that understand binary - those that do, and those that don't

        Comment

        • prj
          S2Forum Zealot
          • Mar 2010
          • 6308
          • Country: Estonia

          #49
          I think you still don't realize, that if you keep beating your car around with 160 lambda trim you will blow it up.
          You have a massive vacuum leak, bad maf, bad fuel pressure, bad injectors or horrible tune. The reason you don't have boost half the time is probably because it's knocking like crazy.

          Good that Audi made these engines so strong, if it would've been a japanese engine it would have thrown a rod by now.

          Long term lambda trim should be between 125 and 131 on a proper tune and a properly running car.
          I would not go more than just barely touching the throttle until you find out the reason for crazy lean running on the car.
          Then again, I have never blown up a customers car.
          Last edited by prj; 1 July 2011, 10:15.
          http://tuner.ee - http://www.facebook.com/tuner.ee

          Comment

          • S2central.net
            Retired OG Mod
            • Jul 2003
            • 16590
            • Country: Northern Ireland

            #50
            The tune is good... had forgotten about the lambda reading being so far off though...

            Seemingly a MAF swap made no difference.

            So a proper leak test is required... then get a fuel pressure gauge... It is the only way to check your pump is flowing strongly and that the fuel pressure regulator is in spec.

            Wouldnt hurt to change fuel filter too.

            You could get the injectors tested and cleaned but I very much doubt all five are fubar.
            Paul Nugent
            Webmaster http://S2central.net
            Administrator http://S2forum.com

            1994 S2 Coupe ABY - aka Project Lazarus
            2001 A6 allroad 2.5TDi - family tank
            2003 S4 Avant 4.2 V8 - daily burble

            Purveyor of HomeFries and Exclusive agent for Samco hose kits (S2/RS2)

            There are only 10 kinds of people that understand binary - those that do, and those that don't

            Comment

            • Dandubz95
              S2Forum Fanatic
              • Apr 2010
              • 67
              • Country: United States

              #51
              I say clear the codes in the ecu and see what the numbers revert to. This will also put the computer into a rich mode until it relearns air/fuel. And please one thing at a time I get this feeling your throwing parts at this thing wishing for an answer. I'm obviously no there but you need to sit down go through a fault tree. Proper diagnoses goes along way to solving the problem right the first time. Oh to check the fuel pressure you a fuel pressure test gauge and you need to hook it up inline to the high pressure feed line, using a tee adapter. Your only going to get running fuel pressure as these cars don't prime the fuel system like other do with the key on.

              Comment

              • montez
                S2Forum Addict
                • May 2010
                • 396
                • Country: England

                #52
                Yeah n75 is working on the output test, but i have the feeling that it may be sticking to i will have it apart to check. I am not throwing parts at the car as I have only replaced what I know is faulty. If the car is running as lean as it says would i not be getting other issues such as the car mis-fireing and knackered spark plugs, I am just questioning if the lambda sensor has failed as it always gives the same reading when i turn the car on?
                1991 Audi S2 Coupe

                Comment

                • montez
                  S2Forum Addict
                  • May 2010
                  • 396
                  • Country: England

                  #53
                  I have just checked the plugs again and it does appear that the engine has been running lean, the lambda sensor has been a recent issue that has come up so I am gonna have to get the fuel system pressure tested.
                  1991 Audi S2 Coupe

                  Comment

                  • prj
                    S2Forum Zealot
                    • Mar 2010
                    • 6308
                    • Country: Estonia

                    #54
                    Originally posted by Dandubz95
                    I say clear the codes in the ecu and see what the numbers revert to. This will also put the computer into a rich mode until it relearns air/fuel.
                    Completely wrong!
                    This ecu does not "relearn air fuel", all it does is run closed loop, and there is no "rich mode"...
                    Open loop operation has no adaptation, if your fuel pressure is off, it'll run 14 afr under boost and only enrich slightly when it hears heavy knock.

                    @Montez
                    Swap the lambda sensor for a known good one and reset your ecu.
                    If your lambda sensor is stuck on lean, then it'll make your car run really bad, because the trim shows right now that your engine is running at an AFR of 18 in closed loop area without lambda correction.
                    http://tuner.ee - http://www.facebook.com/tuner.ee

                    Comment

                    • montez
                      S2Forum Addict
                      • May 2010
                      • 396
                      • Country: England

                      #55
                      Ok, i will get hold of one. are the universal 3 wire lambda sensors ok? I have checked the fuel pump to see if that is ok and it is seeing 13v whilst running.
                      1991 Audi S2 Coupe

                      Comment

                      • prj
                        S2Forum Zealot
                        • Mar 2010
                        • 6308
                        • Country: Estonia

                        #56
                        The stock one is not that expensive if you go via bosch code.
                        It'd be better to swap it for a known working used one first though.
                        http://tuner.ee - http://www.facebook.com/tuner.ee

                        Comment

                        • montez
                          S2Forum Addict
                          • May 2010
                          • 396
                          • Country: England

                          #57
                          Do you know if this part number will work? 035906265B
                          1991 Audi S2 Coupe

                          Comment

                          • montez
                            S2Forum Addict
                            • May 2010
                            • 396
                            • Country: England

                            #58
                            I just started the car from stone cold and the Lambda Control starts off a 128 and by the time the needle is just off the gauge it is hitting 160. I also had the fau
                            lt Lambda sensor intermittent (00537) I cleared them all and only Lambda control limit surpassed came back.
                            1991 Audi S2 Coupe

                            Comment

                            • prj
                              S2Forum Zealot
                              • Mar 2010
                              • 6308
                              • Country: Estonia

                              #59
                              Then either your car is running way lean or your lambda sensor is defect.
                              It will always start off at 128, because lambda control is not turned on until the sensor and the engine are up to temp.
                              http://tuner.ee - http://www.facebook.com/tuner.ee

                              Comment

                              • S2central.net
                                Retired OG Mod
                                • Jul 2003
                                • 16590
                                • Country: Northern Ireland

                                #60
                                I am leaning towards low fuel pressure. Caused by blocked filter or tired pump. Could also be fuel pressure regulator
                                Paul Nugent
                                Webmaster http://S2central.net
                                Administrator http://S2forum.com

                                1994 S2 Coupe ABY - aka Project Lazarus
                                2001 A6 allroad 2.5TDi - family tank
                                2003 S4 Avant 4.2 V8 - daily burble

                                Purveyor of HomeFries and Exclusive agent for Samco hose kits (S2/RS2)

                                There are only 10 kinds of people that understand binary - those that do, and those that don't

                                Comment

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