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 decell 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 ***, 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 refire the engine or to keep the engine running if below 2,000 RPM. If trying to restart it’ll just turn over and nothing will happen, just dead.

The engine will not start again unless I switch the ignition off and back on again...then all is as normal and engine runs perfectly 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 if I rev hard and fast.

However: If I ride the bike smoothly, i.e. slow easy throttling it’ll rev out to red-line all day without an issue what so ever, and will 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 accelerometer is tripping 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 doesn’t.


I’m lost...Is there any Harley engine techs or electricians that may have any ideas of what's causing my power/fuel failure, or is there anybody out there who's experienced the same problem and know what they did to resolved it.

 

You've thrown in a lot of details, some point to an issue and some defy logic.

The switch on and off restart could be a breaker, could be an ignition module, pickup, coils. If you don't have spark when it dies then it's in the ignition system.

The other complaints of running out of gas at higher revs can point to a dirty petcock, cracked fuel pump housing, or a loss of vacuum used to open petcock flow. If carbed a problem with the float, float valve. If EFI could be a computer issue.

If you're not mechanically capable, and don't have a manual or tools and skills needed to fix this I'd recommend you let a mechanic trace the issue.

You could really muck it up tinkering with it.

 

Call Tmax and ask them.

 

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?

 

Guys, when I say the activation number is 4,000 rpm when the throttle is twisted quickly into the 75%-100% TPS region, the engine doesn't die so to speak, it'll continue to rev to red-line once the fault is activated. But once it is activated my DECELL is DEAD. Therefore, I can still ride all day as long as I don't stay in DEACCELERATION mode for too long, allowing the RPM’s to drop below 2,000 rpm, otherwise the engine is DEAD – NOTHING and I than need to reset the ignition for the bike to be normal again.

I found these magic numbers 4,000 and 2,000 through twisting the throttle through many scenarios trying to locate the cause.

I’ve also found that once the fault is activated and I’m decelerating, if held at ‘0’ TPS the engine is dead. However, if I apply enough throttle, bringing the engines RPM above my deceleration RPM’s the engine fires and continues to run normal. Therefore, this indicates that when in decell there isn’t any fuel or spark, yet there is if I continue to throttle. If not throttling in decell it’s evident that there’s no fuel, otherwise the engine would backfire when tying to restart...but it just fires up nicely as if nothing ever happened. The fault also doesn’t cause any error codes in the system.

Strangely though, if I ride sensibly and not twist my throttle quickly and hard into the 75%-100% TPS I don't have a problem at all. If I take it slow and easy the engine still rev's to red-line without triggering the fault, and I’ve since found that if I’m in neutral I’m able to twist the throttle as fast and as hard as I like to 100% and the fault isn’t triggered, it’s only happening while riding, when the engine is under load or the bike is under ‘G’ forces?

NOTE: this isn’t an intermediate issue and nothing on the bike was changed, it just happened over night. My closest memory is that I washed the bike around the same time and my turn signals did play up for a day...the following day everything was fine. But I THINK and I only think this was when my problem appeared or around the same time I do recall decelerating hard from red-line which felt strange at the time?

 

Well it would seem that the TPS is ok since I've never heard of one failing intermittedly, i.e. it either works or it doesn't. ThunderMax communication with you will probably be a big help though that prolly won't happen over the weekend. I don't know with ThunderMax but I've read some ECMs in autos will actually switch between tables to utilize both Alpha-N during one rpm or load range and Speed Density on others. The Alpha-N relies heavily on the TPS and RPM input.

It would seem possible you have a sensor issue OR a VM lookup table (ECM firmware) foobar. Would like to hear the outcome in any case. You mention the TSM but all the schematics I've seen have the input from the MAP, CKP etc feeding back to the ECM. Course at this point nothing can be ruled out. It might be something from another direction.

 

Guys to date I've tried a lot of things trying to find the route cause of my fault. Just to recap on my fault and what's been done is as follows...hopefully someone has other ideas.

I’m experiencing a fault that is causing my engine to be Dead in Decel.
• This fault is not intermittent
• The fault is not generating any error codes
• The fault is triggered by quickly twisting the throttle to 75%-100% TPS and holding to > 4,000 RPM
• This fault is not triggered if quickly twisting the throttle to 75%-100% TPS and holding to < 4,000 RPM
• This fault is not triggered when slowly twisting the throttle rev’n the engine to Red-Line and or Rev-Limiter.
• The fault is only triggered when in motion, i.e. it is not triggered when in neutral.

Once the fault is present the engines decal is dead as though no spark or fuel and or both.
• Engine dies if ‘0’ TPS, clutch applied or stopping.
• Ignition power is still present, i.e. lights, turn signals, speedo, tahco, starter, etc.
• Engine continues to run perfectly if accelerating and will comfortably run all day still able to rev to red-line and or rev-limiter
• Once stopped, engine will not re-start unless ignition is switched off/on to reset ECU (TMax system)
• Once reset the engine runs as though nothing happened...until triggering the fault again

Items checked and or done to-date:
• TPS Sensor – this has been checked and within HD spec
• MAP Sensor – this has been checked and within HD spec
• Crank Sensor – this has been checked and within HD spec
• TMax maps prior to fault tested and fault still present
• TSM – has been checked and all is ok
• TMax 36 pin connector cleaned and greased (does need wriggling now and then for positive connection)
• Battery power – Voltage regulator output checked; +14 volts @ 3,600 rpm
• Bike being washed – all visible electrical plugs have since been cleaned and greased
• TMax AutoSuppot engine run data recorded and sent last week – still waiting for results.

Engine was recently rebuilt 103ci everything was perfect for 6 weeks prior to this fault happening. Overall the engine is still running perfectly, good fuel mileage, plenty of power, no decal popping or back firing is evident.

This fault appeared over-night, nothing was touched, changed or installed prior.

 

Over the weekend I did some more investigating and now a spanner has been thrown in the works.

A long story with how I found this out but I’ve since found that my problem is intermittent and that if once my fault is present I’m also able to flip the kill switch off/on in decel (drag) and the engines dead decell then disappears with the engine returning to normal, rather then having to stop and resent my idnition/Tmax. Therefore, I’m suspecting my problem has nothing to do with my TMax system?

Today I also done a complete TMax firmware and map install, cleaning and removing all prior information and test rode it, although it's raining cats & dogs here at present...and sure enough my problem is intermittent. However, when it does fault as before it is still only caused by the conditions mentioned in my previous postings.

Anyone know what would cause the engine to return to normal once the kill switch is switched off/on as mentioned above? There must be something else playing up causing my dead decell?

 

I have a 2000 Fatboy (our electricals are different though) and had the same issue and it turned out to be a bad wire running to the Bank Angle Sensor. On my bike it's separate from the TSM, yours is integrated, but it is also the only thing I know that can disable the bike and have it reset by turning the ignition on/off.
Your symptoms are the same as what I experienced. Mine would shut off during a shift on a hard accel and also became random. It was a PITA to find but the wire is fixed and the sensor replaced and haven't had an issue since. I hope this helps.

 

Tps?..Doesnt set a code and will test good if it has water in. This has happened to me. Good luck.