Engine Wants to Shut Down after Full Throttle

Discussion in 'Electrical' started by jamesn, Apr 11, 2012.

  1. jamesn

    jamesn Member

    I have a strange problem that I’m unable to resolve and I’m open to any sensible suggestions from those in the know who think they may know what’s causing my problem.

    My engine: a 2004 Softail TC88B modified to a 103 ci, with head work and gear driven cams, and using ThunderMax Autotune. Up until a couple of weeks ago everything was working excellent, perfect idle, a smooth running engine and with plenty of power...and it still is except for the following.

    My problem: If I’m to rev the engine out fast and hard, i.e. 75% - 100% throttle to high RPM (above 4,000) it seems like an electrical fault is activated. Though the engine will continue to run nicely if the RPM is kept above 2,000, but the decell feels dead, it's as if there’s no spark or no fuel on decell, it feels as if a kill switch has been activated. However, if the RPM is kept up above 2,000 everything still works fine, just the decal feeling dead and if I allow the RPM to drop below 2,000, slow down, i.e. to stop at traffic lights the engine dies, it stops dead, no sound, no complaints, no miss firing, no popping or back firing...it just dies in the (EDIT) , dead as a door nail as if a kill switch has been activated....although all of my electrics still work fine, lights, dash, etc, everything is working normal, just there's no spark or fuel to fire the engine or to keep the engine running if below 2,000 RPM.

    The engine will not start again unless I switch the ignition off and back on again...then all is as normal and engine runs perfect again as though nothing ever happened. No fault codes, nothing at all, just the announce of having to stop, switch off and on and restart.

    However: If I ride the bike smoothly, i.e. slow easy throttling it’ll rev out to red-line without an issue what so ever, it'll run all day without a problem at all, with plenty of power and everything smooth as silk....Twist the throttle hard and fast at anytime and the fault is activated again, requiring me to stop and switch the ignition off and back on again.

    My thoughts:
    ThunderMax? How and why everything is working fine, it’s only if I rev hard & fast.
    Fuel pump? The fault would be happening all the time.
    Fuel Filter? Same as above
    Vapour lock? It would be happening if rev’d fast or slow
    Plugs? They’re excellent, new 2 months ago and inspection looks normal
    Poor fuel? I’ve been through 3 tanks from 3 different suppliers and it’s still happening
    Coil? If it fails at hard full throttle it would also fail if rev’d out slow and easy
    TSM-TSS (accelerometer)? Could it be failing when under fast acceleration?
    Water in Electrics? maybe the TSM acceleromter is triping the kill switch, but why does it still run if rev’s are kept up, the kill switch kills the engine, no power at all, it wouldn't continue to run if revs are kept up?
    A lose wire somewhere? why only under hard fast throttling, it would also be happening if on a bumpy road, but it deosn't.

    Please read this...
    HDTalking Language Policy - Harley Davidson Community
    Last edited by a moderator: Apr 11, 2012
  2. dbmg

    dbmg Experienced Member

    It sounds as if the electrical demand can not keep up with the instant on full throttle application. You do not complain of it breaking up just shutting down. Is fueler set up to accompany the build you have?? Any connection at motor loosing power when full throttled, or harness being pinched at frame?? Be sure to do a wiggle test on harnesses.
    Be sure to start with the basics and go from there...:s
  3. SledDog

    SledDog Senior Member Staff Member Moderator

    Perhaps, with the vibration at higher revs, your kill switch is having an issue. Did you have the controls off the handlebars at some point? It might be worth checking. Check your ignition switch also.
    Last edited: Apr 11, 2012
  4. Jack Klarich

    Jack Klarich Guest

  5. TQuentin1

    TQuentin1 Well-Known Member Staff Member Moderator

    I had a problem the other day (and actually about once a month) were my engine will not hold idle. The other day it would actually just die if I let off the throttle. In my case, it is the IAC. You might try cleaning the IAC to see if that helps your situation, although your symptoms include others I did not have. Check here:

    Harley Davidson Community

  6. jamesn

    jamesn Member

    Thanks for your thoughts guys but I'm still not satisfied as all of the ideas mentioned I've checked, done my own Harley mechanical work and rebuilds since mid 1970's, but this problem has me baffled.

    Although we all hate things that happen intermittently to our machines my problem isn't...I can trigger the fault whenever I want, I can also ride all day without triggering it. If I throttle easy the bike comfortably revs to red-line all gears, spooky though when the bikes geared to 180 mph and easily revs to 125 mph in 4th. However, if I want instant power, twisting the throttle hard, my body slung back in the seat, my fault comes into play as soon as I reach approx 4,000 RPM, my decell is then powerless unless I throttle during decell and I then need reset my ignition (off & on) either stopped or while still riding, clutch in, otherwise my engines going to die when I pull over for any reason.

    What I find difficult to understand is that on decell once my fault activated, at '0' throttle the engine is dead as though no spark & no fuel, if I apply throttle during decell the engine still runs normal with spark & fuel.

    I 'THINK' this fault started after washing my bike a couple of weeks ago as I did have a blinker fault after washing the bike, which did go away once dried out. I also 'THINK' that water may have shorted or got into my TSM-TSS.

    Is their anybody able to tell me if a TSM's accelerometer kill switch is activated does it kill power altogether, or does it only kill spark & fuel at '0' throttle. So, if you were to have an accident, your bike fell and the throttle was held on would the engine still run or would it stop no matter what throttle position? I'm not intending on crashing my bike to test it!

    This weekend I'm intending to put my old TSM (prior to TSS) back in to see if it is the cause, it's just that removing my 300 wide tyre as a task in itself...I was hoping that someone may have some idea of the cause before doing so.

    I've spoken to a couple of HD mechanics and I have them also stumped, just one mentioned the TSM which does sound logical but unexplainable?
  7. Hoople

    Hoople Account Removed

    The Bank angle sensor opens the system relay which kills ignition and fuel only. If you trigger the BAS, it will be displayed in the speedo LCD window (with a factory ECM,not sure what happens with ThunderMax). I doubt changing the TSM will help. It sounds like the electronic clocking inside the ThunderMax is getting hung and needs to be rebooted to sort things out. I would look closely at the crank sensor itself & it's connectors at both ends (ECM and pickup). Maybe even swap it out because meter checking it for quality is not reliable. If it stumbles while counting crankshaft flags, it could hang the microprocessor.

    How does the ThunderMax get it's crank shaft phasing in order to perform sequential fuel injection timing? Does it use some kind of cam sensor?
    Can you use a coil other than a Delphi ION sensing coil with a ThunderMax if you wanted to? When you install a ThunderMax, do you loose your ION knock retard subsystem?

    Some systems perform crank shaft phasing during starting. On those systems, if you should loose sync, you must restart the engine to regain sync once again. It almost sounds like that is whats going on.

    I don't know enough about the ThunderMax to know the answers. The key question is how does the ThunderMax phase itself to the crankshaft. These bikes have sequential injectors and the ECM must know the difference between TDC of compression and TDC of valve overlap. Would you know how the ThunderMax accomplishes that?
    Have you called ThunderMax just to ask? It may be something really simple only Thunder People would know.
  8. jamesn

    jamesn Member

    Hoople that's an interesting thought. Re Error codes they're all the same as with the common HD codes and how they display (via Speedo and Blinkers), plus access via PC...I've had no error codes to identify any faults. However, today I sent Thundermax my support data...a recording of the engines maps and setup while engine running and reving. It'll be interesting to hear of their thoughts as I've found they respond to faults very quickly, plus they've been excellent with assisting me setting up my Nitrous and during my 103ci build. Lets see what they respond with and if not satisfied I'll be definatly asking your questions. It's also stange that if I rev the engine hard and fast in neutral the fault doesn't happen...it only happens under load out on the road. Thanks heaps.
  9. Hoople

    Hoople Account Removed

    That is strange.
    So you can mechanically nail the throttle (butterfly is wide open),, stay below 4000 RPM and all is well. Then as speed & RPM increases all remains good until you hit the magic number of 4000 RPM..=> then the engine quits.
    You can mechanically nail the throttle and it's OK.. It is just hitting the 4K RPM mark that turns the engine off.
    But at the same time, you can buzz the engine above 4000 RPM while in neutral and all remain good...

    If that is the case, I would say it's looking more and more toward an issue with the ThunderMax hardware or ThunderMax firmware.
    I have never used or worked with a ThunderMax, but I can tell you that firmware can and does get corrupted. All it takes is a single bit of code to mess things up to the point where the processor hangs. You can never rule that out.
    It is very possible a fresh firmware reload of the TMax would fix a problem like that.

    One other sidebar question I have. Can you be riding along at say 50 MPH in 3rd gear, flip the grip kill switch to off, drag the engine while in gear for a few seconds, flip the grip switch to RUN, and the engine instantly grabs it and picks right back up and runs fine?
    I want to see if the Tmax can re-sync/re-phase on it's own without a normal cranking/starting procedure.
    Don't laugh, some Crane ignitions cannot perform this simple task and must be re-cranked to get re-phased.

    I have some other possible hardware issues on the HD side that can cause this but they are far reaching. Curious to see how this turns out.
  10. jamesn

    jamesn Member

    Hoople, yes this is true.

    I can rev the engine in neutral and nothing happens. Take it out on the road and rev hard below 4,000 rpm and still nothing. Rev hard above 4,000 rpm and fault activates.

    Twist the throttle slow and easy and it'll also not fault throughout all TPS and rpm range...it's only if I twist 75% - 100 % and to above 4,000 rpm.

    The engine doesn't shut down though as it still runs and I'm able to continue riding all day once it has faulted, just as long as I don't allow the rpm's to drop below 2,000...but this is difficult to do when out and about as we do need to stop for traffic lights, etc at some stage and slow down for corners. However, once faulted the engine is dead when de-accellerating (decell). If I keep the revs up once faulted it's fine, just like riding a badly tuned carbie model...keeping the revs up to stop it from stalling. If I let them drop below 2,000 and it's dead and needs rebooting.

    Hope that all makes sence...weird but true.

    I also tried re-loading old ThunderMax maps prior to the fault to see if things changed but it's still the same.

    Looking forward to hearing back from ThunderMax