Surging

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  • TriedStone
    Low Range
    • Apr 2007
    • 81
    #1

    Surging

    Yesterday I purchased my wife a 95 D90 SW. When I test drove it it was surging when trying to accelerate moderately or maintain a steady speed. It almost seems as though the fuel metering is fluctuating. It does not do it at idle or full throttle. It will do it if you rev the engine up to 1800 or 2000 rpms while sitting still. It drastically worsens when you turn the AC on or when you turn the head lights on. So a strong electrical load on the system seems to affect it. The check engine light is not on and there are no codes displayed.

    So far we've cleaned the Mass Air Flow sensor. Checked for loose wire connections in the harness. Checked the alternator which is putting out 13.94v.

    Any suggestions?
    Tags: None
    • spacemutt
      1st Gear
      • Nov 2008
      • 142
      #2
      Coil? Or leads breaking down?

      My 130 rang as rough as a badgers armpit when I got it, but I replaced the plugs, ignition leads, rotor arm and distributor cap and it cured the problem.

        Comment

        • TriedStone
          Low Range
          • Apr 2007
          • 81
          #3
          Originally posted by spacemutt
          Coil? Or leads breaking down?

          My 130 rang as rough as a badgers armpit when I got it, but I replaced the plugs, ignition leads, rotor arm and distributor cap and it cured the problem.
          Thanks! I actually ordered a cap, rotor, wires, and plugs from our hosts earlier in the week. They should be here tomorrow. I don't think thats the problem and I usually don't go about fixing a problem by swapping parts until I actually know what the problem is, however I don't think a tune up is a waste on a truck with 110k.

          I'm still boggled by the fact that a load on the electrical system seems to affect it.

            Comment

            • JayGoss
              1st Gear
              • Nov 2006
              • 146
              #4
              Originally posted by spacemutt
              rang as rough as a badgers armpit
              I'm going to make it a point to use this phrase at least once this week. Awesome.
              1960 Series II SWB
              1994 NAS D90 ST
              1963 SIIa SWB (sold)
              1971 SIIa SWB (sold)
              2000 Disco SII (sold)
              1995 RR Classic (sold)

                Comment

                • kevkon
                  3rd Gear
                  • Aug 2009
                  • 364
                  #5
                  If it's "surging" (as opposed to breaking up) under acceleration or increased load then it more likely is a fuel delivery issue, ie low pressure, blockage, injector(s), sensor.
                  94 D-90 tdi
                  72 Series III

                    Comment

                    • TriedStone
                      Low Range
                      • Apr 2007
                      • 81
                      #6
                      Well... It seems to have been the alternator. The tune up didn't affect it however I did have several wire ends come off during removal, obviously they weren't the best quality.

                      The PO stated that the alternator had just been rebuilt, and even though it tested at 13.94 volts, I couldn't get past the electrical load affecting the surging, so I borrowed one from another truck and Bobs Your Uncle.

                      Thanks guys for the input!

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