My 1994 S4 has recently started giving an alarming problem,the boost seems to be coming in faster and it is showing upto 2.5 bar on the digital gauge,when it hits 2.5 it abruptly cuts out,it also sometimes hesitates/cuts out when showing about 1.2 bar.The car is completly standard 100% standard ecu(never had the lid off),i have changed the wastegate and n75 but hasnt made any difference,there are also no fault codes appearing using vagcom.What should i try next?
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check your wastegate..... seems not to be opened -
It seems like the ECU is not able to get the N75 Wastegate frequency valve to open the wastegate and dump boost in a controllable way. The boost is rising until it hits a level that triggers an overboost protection mode from the ECU (the 1.2 bar = wastegate spring only). As a result, I would still suspect the N75 or the hoses to/from it and/or the connection be between the ECU and the N75. You might want to read through this post and follow the last hyperlink to an N75 output test (to check whether the ECU is communicating to the N75):
Good luck.
Dave F.RS2'd 93 UrS4 5 spd sedan
94 UrS4 V8 6 spd manual avantComment
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As above ...I would check the wiring for the N75 ..think it is the green and yellow wire ?..If this ground to earth it take the turbo to the max and kill it pretty quickly93 S2 Avant Parting
91 URQ RR
02 A4 tdi AvantComment
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I'd bet for a torn wg diaphragm.-Comment
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