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Boost cut after fitting TFSI coils?

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  • Boost cut after fitting TFSI coils?

    1996 S6 AAN, usual RS2 goodies and a screamer

    Been running the RS2 setup for a year with no worries, I just fit a 7a cover and TFSI coils recently and now on full chat you can hear the screamer go from loud to extremely loud for a second and then it cuts boost from 1.8bar to 1.1 and dumps everything out of the wastegate until you switch off and on again.

    Now I've had this before on a previous AAN motor but it only seemed to hit the boost cut in first and occasionally second gear, not sure why the current setup has started doing it when the only thing I've changed is the coils?

    Unless it could be related to the breather setup on the 7a cover?

    Tia

  • #2
    Most likely a boost leak somewhere with those sorts of symptoms. Check the throttle body hose as a potential candidate.
    Greg

    S2Forum.com Administrator & Webmaster

    '93 Coupe with a few tweeks

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    • #3
      Interesting, the only thing I've touched is the breather on the back of the rocker that goes to the inlet, I'll start there! Ta!

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      • #4
        There was a split breather hose but still no joy, still does it, fine again if I flick the key then cuts again as soon as I hit 1.8bar...

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        • #5
          Try check all your vacuum hoses, if the ecu finds a bad or unstable vacuum signal then it will cut boost.
          1996 S2 ABY Silver

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          • #6
            Boost leaks are a nightmare, sometimes you find them in the strangest places, do a search on here there is loads of threads

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            • #7
              I agree I've had leaks in places you wouldn't expect,one from the back of the isv and one from the TPS sensor...a proper boost leak test and a can of plumbers gas leak detector are a must.
              with these cars I reckon a leak test should be done with every oil change
              It's a love/hate relationship with the S2,i love it,it hates me

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              • #8
                Still chasing this one, but now having developed a starting issue because the cam sensor plug is all mashed up, would a bad cam angle signal cause boost cut?

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                • #9
                  From memory (now i could be wrong here) the cam sensor is only used when starting the engine,it shouldn't effect it once it's running.
                  Is your n75 valve in good health?
                  I'd check the ground wires to the im,specifically the ground for the coils since thats the last place things have been touched
                  It's a love/hate relationship with the S2,i love it,it hates me

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                  • #10
                    Also i have a spare cam sensor you could try if it helps
                    It's a love/hate relationship with the S2,i love it,it hates me

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                    • #11
                      Worth checking your coolant temp sensor at the back of the head, G52 I believe.
                      Find me on Instagram @pry4sno
                      2010 Golf Sportwagen TDI /// #farmenwagen
                      2002 Dodge Ram 2500 24v Cummins 4x4
                      1992 80q 20v /// Eventual AAN'd Winter Sled
                      1990 Cq /// Project: Because Racecar

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                      • #12
                        Did you get this sorted? Bad cam sensor will give you boost cut outs.
                        sigpic_________
                        Rob

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                        • #13
                          Never did get to the bottom of this...
                          If I disconnect the banjo fitting to the wastegate, it pulls as it should, whole rev range, every gear BUT at WOT and full boost it will cut all power entirely, just long enough for the car to jerk and pop a huge misfire then carry on.
                          With the banjo like connected the symptoms are as per OP, caps boost until switch off and on again.
                          Can't find any boost leaks, tried unplugging every sensor one by one to see if that helps, all to no avail...

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                          • #14

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                            • #15
                              I had the same problem for years, then I found out about the MAF connections and solved it by unplugging and plugging it for a while but it would always come back, I then bought the gold connectors from a member here and changed all the connectors on the MAF plug but the problem kept as before, I finnaly bought new connectors from Audi that came aready mounted with a length of wire and changed it all again but this time changed the final length of all the wires and cured it for good , I guess that a wire or wires were broken near the MAF plug as they do a very tight turn there.

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