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2007 LF250 High idle, surging, bogging, check engine scrolling

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  • 2007 LF250 High idle, surging, bogging, check engine scrolling

    Hello,
    I have twin F250's, Sunday we ran out fishing and all was normal until we were 10 miles into our return trip. I have the GPH for each engine on my Simrad along with other items like oil PSI, engine temp. I also have the Yamaha square command link gauges for their information. I run the engines very close to the same fuel burn and until this incident, they ran identical RPM. At 10 miles the port engine dropped to 3700 from 4400 RPM. There were no alarms, but the command link was scrolling check engine. I brought both to idle/neutral and turned port off. I lifted it up and checked it for anything abnormal, saw nothing. I restarted it and everything looked fine. I started running in again and the port would not meet the starboard engines RPM at the same fuel burn. Port was about 1000 to 1500 less as far as I could tell. Another 30 minutes went by and it happened again. I checked it again, restarted it and ran in the final 30 miles to the inlet. At the mouth, the tide and wind kicked it up so I dropped down to about 6.5gph burn. A few moments later the port acted up again, the RPM shot up and the burn went to 12gph+ before I grabbed the throttle and pulled it back. Note that the throttle had not moved up on its own, it had not moved at all from where I set it. This cycle repeated 2 twice before I made it to the smooth water and brought the RPM up and ran to the ramp. At the ramp, I noticed the port RPM was 800 at idle, 200 too high. I checked for codes and received a 01. What do I need to do to help you help me? Any assistance is appreciated. I'm well versed in the use of a multimeter and have ordered a Yamaha YDS kit for these engines.

    Thank you for your time. BAP

  • #2
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    • #3
      you need to check for codes while they are active.

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      • #4
        Meaning, check them when it happens I assume.

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        • #5
          yep, have to look when the problem shows up

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          • #6
            If you are going to try to trouble shoot this yourself then you should invest in the proper Yamaha service manual for your engines.

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            • #7
              Update; I used the YDS this weekend. I have 1106 hours on the motor and at 1100.6 hours it recorded code 24 CPS EXH. This would have been while running in last weekend. I ran the engine at idle, 1000rpm and 2000rpm with the engine monitor screen up. At 2k rpm, the engine will reduce RPM after a minute of running, but it doesn't stay reduced. No new codes were generated during this time. I did notice a random and occasional red block flash on the monitor. It was the throttle position sensor 1 & 2, the voltages would jump to a value over 100, but it was so fast I could hardly read it. They would not do it at the same time. Given that I focused on the CPS EXH error 24. I performed the steps to check the sensors 5-34, input voltages and center pin 5v were all good. I rigged up test leads and tested the starb. (in) CPS, which is a suspected good CPS. I know it reads the opposite of the EXH CPS, but it still gave a baseline. I then rigged up the CPS EXH from the port side. It often read correctly, 5v on G & K and .333v on H. Since it is an intermittent problem, I passed the screwdriver in front of it many times. Occasionally the voltage would not recover to 5v from dropping to .333v. It would take maybe 3 to 5 more passes to get it back to 5v on G & K. It would work normally for several more passes, but it would repeat. I'm obviously not moving as quickly as a camshaft, is this normal or is this CPS EXH defective?

              Thank you again for your time.

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              • #8
                I had a very similar problem on my 2006 F250. If I turn the motor off and restart it would then idle properly and run normally. We tried swapping sensors between engines to see if problem would follow but never did. In the end I believe problem was related to low battery voltage.

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