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5.7 GI-C wont reach rpm + negative long term fuel trim -10 to -15 both bank

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  • 5.7 GI-C wont reach rpm + negative long term fuel trim -10 to -15 both bank

    Hi everybody,I did plenty test and I remark negative long term fuel trim all the time and when I put the engine WOT the system immediately come back to open loop , also the max rpm its around 4000 rpm and its suppose to reach 5000 rpm.I test for exhaust restriction without success and I test fuel pump + fuel pressure regulator + I try another MAP sensor without success.I start to suspect o2 sensor ??? Also I like to know if IAT is integrated on MAP ??? somebody have suggestion ??? THANK YOU in advance.Robert

  • #2
    What is engine serial number?
    What scan tool are you using?
    Good Luck Muc

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    • #3
      HI Muc, you"re amazing !!! serial # A223003 10/2012 whit catalyst and I use the Rinda Tech mate pro .THANK YOU

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      • #4
        You can test the o2 sensors with the Techmate. Use the o2 test function.
        Your engine has a TMAP. So yes the IAT is part of the TMAP.

        Do you have any codes in active faults when engine drops out of closed loop?
        What is stored in previous faults and pending faults?
        I can’t remember if the Techmate allows you to see the misfire counter. If it does, what are the numbers?
        Might want to do the injector kill and/or spark kill tests to see that all 8 cylinders are producing the same amount of power.
        Good Luck Muc

        Comment


        • #5
          Hi Muc, I test the o2 whit the techmate pro and they passed the test BUT when the engine is at normal temperature and close loop I saw on the techmate POST CAT TRIM OFF. I have pending and previous ; spn=639 count 1 CAN NETWORK 1 Failure mode =12 Bad intelligent device or component and also in previous spn=3051 count 1 catalyst 2 inactive.I did the injector kill test whit the fuel pressure gauge but the scan tool say nothing ,I just notice the equal drop of fuel pressure for each cylinder.I will perform the spark kill test soon. Can the post o2 sensor can cause my negative long term and max RPM at 4000 RPM ???? Today I raved the engine over 4000 RPM without load and the system stayed in close loop so tomorrow I will test it on the ocean. I did plenty test but I didn't see misfire and I have plenty parameter. BUT I HAVE HARD TIME TO FIND THE RIGHT SPEC FOR MY ENGINE on the net 10/2012. I called volvo penta dealer and nothing is available . Do you have a recommendation ??? THANK YOU VERY MUCH AGAIN FOR YOUR HELP .

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          • #6
            What section in the techmate do you see POST CAT TRIM OFF? That isn’t something I have seen come up on Diacom. But I don’t have much experience with a techmate. If it is a fault, you should get a DTC or SPN.
            You should not be able to do a spark kill test with the techmate on a catalyzed engine. The injector kill test is what you do.
            Did you do a Injector KILL test with a pressure gauge connected? That’s not how that test works.
            You should be doing a injector FIRE test if you have a pressure gauge installed. The injector fire test is very difficult to do correctly. The service manual for your engine controller does not explain how to do this test. The manual is written for a trained technician and assumes that you know how to do the test properly. I’m not trying to be a jerk, but do you have the training or knowledge to troubleshoot this system?
            What Spec are you looking for?
            I hope you have a copy of Workshop Manual EGC Diagnostics P/N 7749393 If you don’t, you need to stop right now and get one.
            I assume the problem your trying to fix is the max 4,000 RPM? If so have you completely ruled out these 14 items? They are all things that must be addressed before you will get data from a scan tool that will help.
            Engine Won’t Reach Operating RPM
            1. Fuel type or octane
            2. Propeller pitch or diameter, damaged blades, slipping hub
            3. Crankcase oil level
            4. Marine growth on hull and drive
            5. Wrong Sterndrive gear ratio
            6. Operating at high altitude
            7. Restricted air intake
            8. Restricted exhaust outlets in engine, transom bracket or drive
            9. Poor cylinder compression
            10. Fuel pump pressure and vacuum
            11. Boat overloaded, or load improperly placed
            12. Engine overheating
            13. Engine timing and ignition system operation
            14. Remote control cables and linkage for proper attachment and
            travel
            Good Luck Muc

            Comment


            • #7
              Hi Muc I saw the post cat trim off in the catalyst section of the tecmate ,the same section where I can see the close loop switching back open loop over 3000 RPM, I forgot to said at close loop mode its indicate on the techmate all the time CLOSED + ADAPT ??? do you know if its normal or because of the issue.Also im not trained and this stuff is new for me but I learn a lot everyday and I understand the fuel trim concept and I learn a lot using the techmate pro and all the info on the web.I ruled almost everything on the list and I WAIT for the good EGC manual.I live Providenciales (island)so I must fix that that myself.Thank you for the info and your help.ENJOY

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              • #8
                The spec I looking for is all the parameter of sensor,vacuum,voltage, EX; cam retard at 12,5 is it normal ?. I use a EFI water test sheet I found on the net to note all the parameter I can access in my techmate pro.Also my vacuum is a bit low on idle 15 HG. I still suspect my post cat o2. THANKS AGAIN

                Comment


                • #9
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                  Cam retard 12° to 15° is normal.

                  Vacuum 15" is on low side (but still considered normal) but you must take into account the BARO reading before you make that decision.

                  Some of the specs you are looking for are in the manual. But most of them are numbers that change with the local conditions. Like altitude, fuel quality, temperature and humidity are just a few. Because of the many variables involved. The tech is assumed to know what numbers to be looking for based on experience.

                  I wouldn't worry about the post cat O2. It's main job on your engine is to monitor the catalytic converter efficiency. The pre cat O2 is what controls the fuel trim. A failed Post-cat O2 sensor can NOT cause an engine running problem.

                  Long term fuel trim -10% to -15% is normal. It can go over 35% negative or positive before a code is set.
                  A perfect running engine (at steady speed, steady load) would have a long term fuel trim reading between +15% and -15%.

                  Post cat trim off is normal. The post cat O2 only changes fuel trim to make slight adjustments to increase catalyst efficiency
                  .
                  CLOSED + ADAPT is normal. It just means that the engine is in closed loop and is now able to write the short term fuel trim to the long term fuel trim tables.

                  Your engine should switch from closed loop to open loop when you reach higher RPMs. That's how the system functions.

                  If you want to post the test sheets you have, I can take a look at them to see if anything looks wrong. But so far everything you have posted leads me back to this list.

                  Engine Won’t Reach Operating RPM
                  1. Fuel type or octane
                  2. Propeller pitch or diameter, damaged blades, slipping hub
                  3. Crankcase oil level
                  4. Marine growth on hull and drive
                  5. Wrong Sterndrive gear ratio
                  6. Operating at high altitude
                  7. Restricted air intake
                  8. Restricted exhaust outlets in engine, transom bracket or drive
                  9. Poor cylinder compression
                  10. Fuel pump pressure and vacuum
                  11. Boat overloaded, or load improperly placed
                  12. Engine overheating
                  13. Engine timing and ignition system operation
                  14. Remote control cables and linkage for proper attachment and
                  travel

                  You really need to think about what could have changed from when the engine would reach full RPM and now that the engine won't go above 4,000 RPM
                  You NEED to rule out ALL 14 items.
                  Good Luck Muc

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