Possible motor swap, need second opinion!?

So if you see the my previous post my car has been misfiring after installing new spark plugs. I had a mobile mechanic come by and he ran a compression test all cylinders showed 150 except two that ran around 120. The mechanic said I am going to need a new motor. I am skeptical as my car was running perfectly before putting new spark plugs in. I already spent a descent amount of money on figuring this out changing coils, MAFs, new spark plugs, etc. I don’t know if he’s pulling my leg but I know that Las Vegas mechanics have a shady reputation. Any answers appreciated! Again it’s a 2011 Infiniti G25.

7 Answers

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  • not
    Lv 7
    4 months ago

    I'd have a real mechanic diagnose the problem. 

  • 4 months ago

    If you used NGK or Denso iridium spark plugs the spark plugs should not be the problem. Bosch or Autolite spark plugs will cause misfires even if new. 

    You need a $3000 scan tool to read the engine data to make sure all the sensors are working with in spec. The camshaft and crankshaft correlational needs to be verified to make sure the timing isn't out of time. thse motors have a common issue with timing chains stretching and cam advance actuators sticking so that may be your problem with the used motor. 

    Source(s): Mitsubishi Master Tech / Infiniti Tech
  • 4 months ago

    Although the 2 cylinders with 120 compressions are not optimal it would not necessitate changing the engine.  The question is whey are those two so much lower.  Are they next to each other, if so you may have a leak between then in the head gasket.  You need to have a scan tool hooked up to see if any of the cylinders are misfiring, if the car ran good before changing the plugs I would think that something happened when you did that.

  • 4 months ago

    Is this the one where you claimed a screwdriver bit fell into a cylinder? Did you get it out before turning the engine over?

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  • Anonymous
    4 months ago

    Check for trouble codes again.  Check for spark on the misfiring cylinder/s.  Check if the injectors are firing and check injector pulse.  Check crank sensor output on a scope.  Ask around for a competent garage.

  • Dan
    Lv 5
    4 months ago

    The spark plugs were damaged when they were installed, it's obvious. Have a pro install new plugs, make sure they're started with a piece of rubber hose, never dropped in on the end of an extension.

  • Matt
    Lv 6
    4 months ago

    I had my spark plugs replaced by a garage a few years back and it turned out they didn't hook the wires back up correctly.  You might want to look into that because new spark plugs wouldn't cause you to have that problem.  I took it to another garage and after they hooked the spark plug wires correctly the car ran great.

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