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Aloha! Poor Cold Start/Running.

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  • Aloha! Poor Cold Start/Running.

    Is it normal for a "cold start" (keep in mind it's high 70's, low 80's here) to begin with an instant start-up, followed by a serious drop in idle to 500rpm or less (no stall), then a rise in idle to 1300rpm or so?
    Additionally, is a jerky first few miles until up to temp normal?
    If not, any ideas?
    Mahalo.

  • #2
    Sounds like your vacuum leak... or idle air control...

    When I start mine, it can be a little rough for the first 10 seconds, but it smooths out pretty quickly. I have about 200K miles on my car, so I feel it deserves a little time to wake up...
    96 Montego - FFS ColdSide, 97 Black & Tan, 90 White
    www.miatacare.com

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    • #3
      Mahalo Bogey.
      I actually heard a “click” and the idle went to normal. Does IAC operate via relay?

      Also, long hose going from IAC to intake tube is VERY noisy all the time…pinch the hose and it quiets down.?

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      • #4
        The valve may click. Not sure why it would be noisy. Most of the time I believe it should be closed. This could explain high idle.
        96 Montego - FFS ColdSide, 97 Black & Tan, 90 White
        www.miatacare.com

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        • #5
          Did finding your vacuum leak solve this issue?
          96 Montego - FFS ColdSide, 97 Black & Tan, 90 White
          www.miatacare.com

          Comment


          • #6
            Still chasing poor cold drivability issue…..it’s livable, but annoying.
            I sure would love it if someone had a “current” hose routing diagram….perhaps I’ll post the question here .

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            • #7
              The problem is the oil. I will guess that you are using synthetic oil and possibly a heavy weight. When Mazda did the VVT on the 01-05, they ran into the cold start issue as cold oil doesn't flow well and the VVT is hydraulic and runs off of the engine oil. Their solution was to insert a set of butterflies in the air intake runners with small holes in them. This was called VTCS (Variable Tumble Control System). It cause the air to tumble into the cylindersa nd that allowed the engine to run smooth while cold bu make limited power. When the water got up to operating temperature, the valves opened to full runners and allowed more air/more power. The temperature delay was to give the oil time to warm up a bit and flow better so the VVT could respond faster. Along comes the supercharger and it can make instant power and move a lot of air instantly and the VVT just can't move with coild oil. Personally, I think the fact that you can't make power with cold slow flowing oil is a good thing.

              Just so you know, I have both a real water temperature gauge and a real oil temperature gauge. In cold weather, it can take 2-3 minutes for the water to get to a minum temperature of 160F. At that point, it can take another 3 minutes or so for the oil temperature to get above 120F. Assuming I am correct and you are running synthetic oil, changinging to a lighter weight, non-synthetic oil will shorten the time for the oil to warm enough for the VVT to be able to move fast enough to not cause grief. However, I think a good synthetic oil is worth the 2-4 minutes of poor driveability.

              Tom
              sigpic


              1990 with FFS Coldside. At least 260 WHP NON-INTERCOOLED

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