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AAN S4 started ignition knock suddenly

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  • AAN S4 started ignition knock suddenly

    1994 s4 with rs2 manifold and turbo. Intended acceleration tune with 300kpa map sensor running original injectors. So it started pinging lightly just as boost builds, then as more boost builds so does the pinging. There is no missing or bucking. It still runs smooth, but has become quite boring running non boosted now!

    My diagnosis thus far:
    Fuel pressure at idle 55 psi rising with boost. I did not push much boost due to pinging
    I have followed the bentley procedure for testing the MAF, all is in spec (measured resistance between pins 1&2 then voltage with engine running). I have unplugged the maf and it runs very rough.
    I removed the map sensor from the ecu, supplied 5v , ground, and varied pressure to measure output voltage. Output is perfect with the data sheet for Map sensor.
    I have ohmed the intake air temp, and coolant temp sensors. Both are in spec.
    I suspected possible bad gas, but have run that tank near dry and refilled with premium (93 USA octane E10) with no change.

    Parts replaced so far
    Timing belt, tensioner, water pump, air filter, fuel filter, oxygen sensor, spark plugs.

    Any help would be much appreciated before I start throwing parts at it.

  • #2
    Have pulled any fault codes. I would have to think that the G61 and G66 knock sensors are not functioning properly.

    G61 and G66 Knock Sensor info:

    http://forums.quattroworld.com/s4s6/msgs/21047.phtml

    RS2'd 93 UrS4 5 spd sedan
    94 UrS4 V8 6 spd manual avant

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    • #3
      No codes are present. I may try a volvo 960 maf, or I might get a DW300 fuel pump since I will need to upgrade anyway.

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