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Thread: MR1 Rough Idle

  1. #1
    thompsdw's Avatar
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    MR1 Rough Idle

    Hi guys. This seemed the best place to post a question on a NA MR-1 marine engine. This is in a Yamaha boat, but I wanted to see if I could get some tips here given it is the same engine in the VX110. It seems like the most common issue for rough idle on a MR-1 is related to spark. I changed all my plugs and still have a noticably rougher idle and noise on one of the two engines. I changed all the plugs and did a resistance check on the COPs. The same problem persists. The air filter is fine with no oil exposure.

    Can you guys give me some tips on what to check next?


  2. #2
    If you have access to an infra-red thermometer you could check exhaust temp of each cylinder at the exhaust manifold while the engine is running at an idle. Look for the lowest temp and there is your problem (dead) cylinder. It could be a possible injector not being pulsed or a misfiring plug due to over or under gapping. Try swapping the spark plug out of the low temp cylinder into another cyinder and see if the problem follows it there. If not try swapping the plug wire around or OHM out the plug wires and see if they're consistant. If all cylinders are at the same temp + or - 15 deg or so I'd then look into a timing problem and dig into the crank/cam position sensor. Just my .02 Let me know how you make out.

  3. #3
    thompsdw's Avatar
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    Here is what I have done thus far:

    1) Changed the plugs on both engines.
    2) Took compression readings on both engines.
    3) Used the diagnostic software to ready both engines.
    4) Checked the oil level in each engine and visually inspected the air filter.
    5) Checked the resistance of the COPs (no plug wires on this one).

    Here is the engine data (interesting that the values are the exact same):
    4.Engine Monitor
    Monitor Item (DATA) Result Port Result Starboard
    Engine speed 1605 1605
    Intake pressure 36.44 36.44
    Intake pressure 10.87 10.87
    Throttle position sensor 1 0.684 0.684
    Throttle valve opening (0-90) 3.9 3.9
    Throttle position sensor 2 2.686 2.686
    Accelerator position sensor 1 0.703 0.703
    Accelerator position sensor 2 0.63 0.63
    Atmospheric pressure 986.9 986.9
    Atmospheric pressure 29.2 29.2
    Ignition timing BTDC 6 BTDC 6
    Battery voltage (12-16) 14.47 14.47
    Fuel injection duration 2.44 2.44
    Engine temperature (below 130) 38 38
    Engine temperature (below 266) 100 100
    Intake temperature 27.5 27.5
    Intake temperature 81.5 81.5

    Here are the compression readings (note that the 190 psi is on the engine running smooth):
    Compression Test
    Cylinder Port Starboard
    1 167.0 165.0
    2 167.0 170.0
    3 190.0 167.0
    4 170.0 170.0

  4. #4
    Take the time to smile sirbreaksalot's Avatar
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    Quote Originally Posted by thompsdw View Post
    Here is what I have done thus far:

    1) Changed the plugs on both engines.
    2) Took compression readings on both engines.
    3) Used the diagnostic software to ready both engines.
    4) Checked the oil level in each engine and visually inspected the air filter.
    5) Checked the resistance of the COPs (no plug wires on this one).

    Here is the engine data (interesting that the values are the exact same):
    4.Engine Monitor
    Monitor Item (DATA) Result Port Result Starboard
    Engine speed 1605 1605
    Intake pressure 36.44 36.44
    Intake pressure 10.87 10.87
    Throttle position sensor 1 0.684 0.684
    Throttle valve opening (0-90) 3.9 3.9
    Throttle position sensor 2 2.686 2.686
    Accelerator position sensor 1 0.703 0.703
    Accelerator position sensor 2 0.63 0.63
    Atmospheric pressure 986.9 986.9
    Atmospheric pressure 29.2 29.2
    Ignition timing BTDC 6 BTDC 6
    Battery voltage (12-16) 14.47 14.47
    Fuel injection duration 2.44 2.44
    Engine temperature (below 130) 38 38
    Engine temperature (below 266) 100 100
    Intake temperature 27.5 27.5
    Intake temperature 81.5 81.5

    Here are the compression readings (note that the 190 psi is on the engine running smooth):
    Compression Test
    Cylinder Port Starboard
    1 167.0 165.0
    2 167.0 170.0
    3 190.0 167.0
    4 170.0 170.0
    HOW MANY HRS?

    HAVE YOU CHECKED BY DICONNECTING 1 INJECTOR AT A TIME TO SEE WHICH CYLINDER IS LAZY OR CAUSING THE WOBBLE AT IDLE,,

    AS SAID BEFORE ONCE YOU HAVE FOUND THE CYLINDER START CHANGING THINGS,

    i SEE U ALREADY CHANGED HEAPS OF THINGS

    BUT TODATE HAVE U CHANGED THE INJECTORS OVER MAY BE EASIER TO SWAP HOLE RAIL,

    IF MISSFIRE FOLLOWS RAIL/INJECTOR THERES YOU DRAMA

    WARREN

  5. #5
    if u have access to YDS do a drop test to rull out an injector also do aleakdown, pm me if u need any help

  6. #6
    thompsdw's Avatar
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    21 hours on the engine. I did do a drop test on each cylinder to see if there was a cylinder that didn't impact the engine singificantly. I didn't see any difference as the cylinders were dropped (from cylinder to cylinder). The engine did seem to run noticably rougher when each individual cylinder dropped. I was thinking of getting an inline spark tester next to check the COPs. The resistance checks were fine.

  7. #7
    Didn't they have an intake manifold issue on the VX110 motor?

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