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Missing at idle, does not pull as hard as it should..

Posted by dyetrying91, Aug 29, 2010

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  1. dyetrying91

    dyetrying91 Proven Member

    107
    1
    Joined Jul 2, 2009
    North Haven, Connecticut
    I posted a thread about 2 weeks ago and got some decent help, since then, I have an update, and a few more questions.

    Basically, I have low vacuum at idle, idle walks around like crazy when hot, (650-2100), it's not idle surge. I'm pretty sure the idle issue is my TPS being out of adjustment.

    Despite the low vacuum, it misses at idle, fairly bad, below is a video I took of the problem..

    <object width="480" height="385"><param name="movie" value="http://www.youtube.com/v/uSpbfP_0Cr0?fs=1&amp;hl=en_US"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/uSpbfP_0Cr0?fs=1&amp;hl=en_US" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="480" height="385"></embed></object>

    Here is one more video I took after a brief stint at 80 or so on the highway,

    <object width="480" height="385"><param name="movie" value="http://www.youtube.com/v/xmequfF6YS4?fs=1&amp;hl=en_US"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/xmequfF6YS4?fs=1&amp;hl=en_US" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="480" height="385"></embed></object>

    Don't mind the oil pressure gauge not working, the wire caught a piece of road debris under the car.

    Since I posted the last thread, I have done the following:

    1. Boost leak test, only found 2 small leaks @ 32 psi. One at the TB seal and another at the BoV.
    2. Compression was 141, 161, 158, 160 on a dry test. I have reason to believe that the cylinder 1 ring is getting worn, its at 94k miles on the stock block and it was running 18psi on an 18g for quite some time.
    3. Checked mechanical timing, everything looked perfect.
    4. Changed plugs/wires, tried both 6's and 7's. Have 7s in it now.
    5. Found a small exhaust leak at the manifold/head from a missing manifold bolt, replacing it tonight.

    I'm completely at a loss here as to what it could be. The head has less than 1000 miles on it and came off of a running car. Any help is greatly appreciated.

    -Dave
     

    135  0

    1998 Mitsubishi Eclipse GST
    · 2G DSM
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  2. smrogers5771

    smrogers5771 Proven Member

    97
    3
    Joined Jul 22, 2010
    NorthernCambria, Pennsylvania
    id say boost leak...
     

    464  0

    1996 Mitsubishi Eclipse GSX
    · 2G DSM
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  3. dyetrying91

    dyetrying91 Proven Member

    107
    1
    Joined Jul 2, 2009
    North Haven, Connecticut
    I ran a boost leak test with my boost guage at 30psi with no leaks besides tiny ones at throttle body and BOV. I really don't think I have a boost leak large enough to cause these kinds of issues.

    Spent the past 2 hours looking for vacuum leaks. I am at a loss here. Should I start looking at fuel? Possibly the ECU?
     

    135  0

    1998 Mitsubishi Eclipse GST
    · 2G DSM
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  4. RLPerformance

    RLPerformance Proven Member

    64
    2
    Joined Aug 13, 2010
    Commerce, Michigan
    Does it miss at cruising speeds too? or only at idle? Its not throwing any CEL? You could still have a bad coil pack causing a miss but it will often get worse as you drive the car. A vacuum leak will usually cause the car to idle higher and not fluctuate too much. FIAV - Fast idle air valve can cause rough idle issues. How did the old plugs look that you pulled out? Did one look different than the others (all black - fouled, all white - too lean)?
     
  5. dyetrying91

    dyetrying91 Proven Member

    107
    1
    Joined Jul 2, 2009
    North Haven, Connecticut
    It's only at idle and only at decel above 3k rpm, say a shift down from 4th to third at 55 or so. Old plugs looked normal, neither rich nor lean.
     

    135  0

    1998 Mitsubishi Eclipse GST
    · 2G DSM
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  6. joseph95

    joseph95 Probationary Member

    7
    0
    Joined Dec 6, 2009
    antioch, Tennessee
    check your throttle body for leaks, the bolts will look wet, also could be biss screw, my problem was throttle body shaft seals and gaskets.
     

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