Brain picking time

Discussion in 'Engine & Performance' started by Boltslinger, Aug 6, 2018.

  1. Boltslinger

    Boltslinger Member

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    2000 Expy 5.4 2v. Just rebuilt engine and trans. Basically everything is new, inside and out.
    Only non stick item is 20+ pistons.
    Having a real performance issue, and electrical issue. Maybe related? Been through all the wiring, ohms and VD.
    Chasing a random miss. Just jumps around to different cylinders. Not enough to throw a code, but I can see it on the scanner graph. All cylindersare at 220psi even. Maybe I should run a higher octane with that comp? Am I chasing pre detonation?
    Electrical issue: At idle, blower speed goes way down and I have far less hp with ac on. My ac isn't really cooling like it should. Ac compressor doesn't seem like its binding spinning it by hand with clutch engauged.
    Any thoughts?
     
  2. Trainmaster

    Trainmaster Full Access Members

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    Check your battery and alternator. It's a long shot but low voltage could do what you describe.
     
  3. Black

    Black Full Access Members

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    Sure all your vacuum lines got reconnected properly?
     
  4. Boltslinger

    Boltslinger Member

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    Yes
     
  5. 1955moose

    1955moose Full Access Members

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    220 psi cylinder pressure is high for a stock 9 to 1 ratio. Did you put in higher domed pistons? Normal stock compression is usually around 170-185 tops. Definitely run 92 octane. The bouncing misfire is kinda weird. Might want to swap out the crank position sensor. A cracked or shorted one could be contributing to your problem. Would explain the bouncing from cylinder to cylinder. Their cheap enough to replace. As far as the AC, make sure you have a full charge, and your blender doors are opening/closing proper, and compressor, AC clutch, are up to snuff, including pressure switches.

    Sent from my N9131 using Tapatalk
     
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  6. Boltslinger

    Boltslinger Member

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    Think I will throw a crank sensor on it, hope your right. Engine load graph is pretty jumpy. Thanks.
    Didn't think about the likely weak aftermarket sensor I put on about a year ago.
    As far as how I got the comp up to 220, it just worked out that way. The pistons aren't anything special, just +20. Probably the machinist that worked the heads and decked the block.
    Will do it tomorrow and post back.
     
  7. 1955moose

    1955moose Full Access Members

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    He probably shaved the heads to get flat again. That and decking the block would have raised it up. Your kinda stuck running high octane fuel though. On the bright side the raised compression ratio probably bumped the horsepower and torque by a few points. It will definitely have more oomph!

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