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  1. #1
    Vern's Avatar
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    Idle rpm and idle AFR bouncing around - ideas?

    I have about 10 hours on a fresh motor in my 2005 RXP, running Duke's 9200 rpm ECU with Riva RRFPR, same setup as last year. Ran great so far this year, no issues, but last weekend my idle suddenly started surging up and down, and my idle - low rpms AFR was bouncing all around too, going very lean, but varying from 13s to 16s, all without touching the throttle.

    I checked for boost or vacuum leaks, none. Fresh plugs the weekend before, and fuel pressure on the gauge looked very steady, so I don't think it is the fuel pump. This ECU and the 80s are set to work at 40psi static and that is exactly where the fuel pressure gauge stayed, no moving there. I ran the same pressure all last year and so far this year, with good AFRs.

    My guesses are the MATS sensor, or IAC maybe, but the combination of swinging idle rpms and swinging AFR both is something I have not run into before. Thoughts or ideas on what it might be or what I should check this weekend?


  2. #2
    Got Boost? psycho rxp's Avatar
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    Check the IC for leaks

  3. #3
    Moderator beerdart's Avatar
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    Do you have access to Candoo if so check your MAP readings.

  4. #4
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    I was just gonna say to check your MAP sensor, see if its got any debris...and check your idle bypass, make sure its moving freely...

    On a side note, I'll be near you next weekend...Down in Hartford area.

  5. #5
    Moderator beerdart's Avatar
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    Hit me up im 30 min from Hartford.

  6. #6
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    Hartford, MI...About an hour south of Vern.

  7. #7
    Moderator beerdart's Avatar
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    Quote Originally Posted by Danny View Post
    Hartford, MI...About an hour south of Vern.
    Oh hit me up anyhoo

  8. #8
    Vern's Avatar
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    Thanks for the input. I will pull the IC hoses and check for water and signs of water, and ohm out the MATS on the ski. I actually have a spare green brand new MATS sensor too, so I can compare how they ohm.

    If it is the MATS sensor, are there tips to remove them without issues? I had heard of people stripping threads or messing up the intake manifold when removing them sometimes ...

    I don't have Candoo, but Jim does, but I would have to pull the ski off the lift and trailer it to get there. I will check the other stuff and compare the two sensors and see what I find first. No codes or warnings, just surging up and down and going lean to rich.

    Danny, I looked up Hartford, had not heard of it before. Looks like it is a bit south of me, maybe 1.5 hrs. I live in Belmont, MI now and ski in Grand Haven, MI but we have family in South Haven too, which is pretty close to Hartford.

  9. #9
    AtoMIC_OraNGE greenbullet's Avatar
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    reset TPS using candoo vern...

  10. #10
    Vern's Avatar
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    Quote Originally Posted by greenbullet View Post
    reset TPS using candoo vern...
    Makes sense too, but it is my original TB and has always worked well prior to this. If nothing obvious pops out on my other checks, I may have to pull it out and bring it to Jim and hook it up to Candoo.

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