EFI Engine Surge

Discussion in 'Engine, Fuel and Exhaust' started by klinkcol, May 26, 2009.

  1. klinkcol

    klinkcol Member

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    EFI Engine Surge/RPM flux

    Problem: At steady throttle when driven approximately 25 MPH in second gear, for about 1.5 miles, RPM drops and returns to original value. It appears the engine is leaning out and when you increase the throttle, RPM’s increase. If you remain at the same MPH, the drop in RPM increases to the point of the bike bucking violently. At this point, the only way to stop it is to slip the clutch increasing RPM’s. It also happens in First gear, just at a lower MPH. The bike remains un-drivable until you start is up when the engine cools down (First start of the day). Driving the bike at higher RPM’s, at a steady RPM, there is still a RPM flux, but it is drivable.

    Bike: 2006 Dyna FXDI. 100% Stock. 35K Miles. Driven in all weather, all year round. North East Florida area.

    History: Three times the engine quit on me while driving, just like the engine kill switch was on (MPH went to Zero, but everything else worked). After cycling the kill switch, the engine starts. The bike was in storage for Five, Two, Three, then Two months, driven only 10 miles between each period. I put fuel stabilizer in the tank during this period. The bike has always had a slight engine RPM flux at low RPM steady throttle.

    About 500 miles after my final storage period, the RPM flux started to get worse. When you increased the throttle it went back to normal. Varying the throttle there is no RPM flux. Within the next 500 miles it was not drivable (above issue). I replaced the spark plugs and it returned to normal. The plugs looked fine for an EFI bike. After the next 500 miles, the RPM flux returned to where it is today.

    Things done since this problem appeared: Replaced the battery (was not taking a full charge), air filter, fuel filter, spark plugs,(X2), drained the fuel and replaced with new fuel, tried Screaming Eagle spark plug wires (no change and the resistance was the same and within HD limits), measured the resistance from the ECU to respective plugs for all EFI wires (with the exception of the idle control solenoid) with no faults found, coil resistance checks good, used WD40 and Propane around the intake manifold (no change in RPM). The local HD dealer, checked the fuel pressure and hooked up a scanner and found no faults. I also disconnected both O2 sensors and it ran the same (no codes or check engine light). I removed the engine temperature sensor from the engine and plugged it back in, thinking the computer would not register the engine temperature. I then got injector high codes for both injectors. There has never been a check engine during engine operations with the exception of start up which is normal and no codes found with the exception of the previous.

    Thoughts: Engine is running lean at low engine loads and low RPM's. Possibly O2 sensors. Ever since this has taken place, I have used 10% ethanol 93 octane fuel (Only fuel available in Florida).
     
    Last edited: May 28, 2009
  2. glider

    glider Veteran Member

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    Have you checked the fuel pressure and flow?
     
  3. klinkcol

    klinkcol Member

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    HD said fuel pressure was good. I believe the fuel flow is good, seeing that the engine runs normal during high RPM and full throttle.
     
  4. glider

    glider Veteran Member

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    Are you sure it's the engine and not the primary chain shipping from a bad adjustment?
     
  5. klinkcol

    klinkcol Member

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    The RPM flux is noted in neutral at what I believe is 2000 RPM. The RPM flux starts out with a deceleration first. Full throttle high RPM no RPM flux. Also noted when this problem starts, the engine pings during high loads. Fuel level has no change in this condition. I have had chains and clutches slip before and I do not believe it is it.

    This may sound crazy. I took an S&S carburetor off my Sportster and held it next to the throttle body, with the EFI throttle open at 100%. Now there were many air leaks, but the bike started up normal and had little if not no RPM flux at approximately 2000 RPM. Of course, I could not take it for a ride, but when I removed the carburetor and ran on fuel injection the surge came back.
     
    Last edited: May 27, 2009
  6. Lancer

    Lancer Junior Member

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    Do you have any type of fuel management device? My Ultra would surge similar to yours when I first bought it. Not a bad surge but noticeable. I put XIED's on it and the problem went away. I have since gone with a TFI (full stage 1) I was happy with the XIED's, even happier with the TFI.
     
  7. klinkcol

    klinkcol Member

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    No fuel management devices. 100% Stock. That is probably my next step, getting something that can read out all sensors while driving. I believe the engine is running lean at low RPM’s and low engine loads, possibly the O2 or MAP sensors.
     
  8. bfmitch

    bfmitch Active Member

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    Did you say that you disconnected the O2 sensors and didn't get a check engine light or a code?

    The ECU should go into open loop mode when you disconnect the sensors, so the bike should run. But, without resistors in place of the O2 sensors, to fool the ECU into thinking the O2 sensors were installed, you should get a warning or a code.

    Did you buy the bike new? Maybe some previous owner rigged O2 sensor bypass resistors back in the harness somewhere when they put on a fuel management device.

    Have you cleaned the MAP sensor wire?

    That business about checking it with the carburetor is kind of weird. Good idea though. Are you saying that the carburetor was supplying the fuel air mixture for the engine? Why would you hold the EFI throttle wide open? I would think that you would want the fuel injectors completely inactive so the carb would be handling all the fuel mixture. I would have thought you'd disconnect the injectors while doing this.
     
  9. klinkcol

    klinkcol Member

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    No check engine light and no codes after running with both o2 sensors disconnected. I did this on two occasions and ran the bike for about five miles with the same RPM flux. I believe it should get a check engine light and codes when they are disconnected. I am the original owner and only the local HD dealer has had the bike a few times to fix some warranty issues.

    How do you clean the MAP sensor wire? I do not recall seeing this procedure in the Maintenance and Electrical manual. Will recheck both manuals tonight. There is a sensor wire for Mass Airflow sensors used on EFI GM and Ford vehicles. I do not recall one for HD Motorcycles. My thought is this problem can be MAP, TPS, O2, Computer or anything between.

    My thinking for running with the carburetor was to see if it was a fuel or ignition issue. HD dealer already said everything checks fine with there scanner. I opened up the throttle to 100% and applied the friction lock, so it would not block fuel and inputs from the carburetor and then pulled the fuel pump fuse so it would not supply any fuel from the injectors. I do not believe doing this eliminates anything but I am leaning towards Fuel side.

    My next step is to bring it back to the dealer for one more check. When ever I get this problem resolved, I will share the answer with all.
     
  10. TQuentin1

    TQuentin1 Well-Known Member Staff Member Moderator

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    When you pulled the speed sensor out did it look like it had an afro? Even if you got all that off of there, it may still be worth swapping that out. Not too expensive, and an easy install.

    You did check out the fuel delivery, right? I had pinholes in the convoluted tubing inside the tank on a couple of occasions. But that is a very pronounced set of symptoms that are hard to miss (it's like running out of fuel). Tattletail is the "psssst" sound in the tank take the cap off and listen) longer then just the charge up time especially when the tank level is low.

    TQ