I have a strange problem that I’m unable to resolve and I’m open to any suggestions from those in the know or those who have experienced a similar problem. I’ve also posted this in the forums engine section but I’m still no closer to resolving the fault.

My engine: a 2004 Softail TC88B modified to a 103 ci, head work, 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. Note: prior to the fault nothing on the bike was touched or changed...this fault happened over night.

My problem: If I’m to rev the engine out fast and hard into the 75% - 100% throttle position to high RPM (4,000 and above) it triggers a fault and the engine dies.

When I say the fault activation is above 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 has been activated my DECELL is DEAD. Therefore, I can still ride all day after the fault is activated just as long as I don't stay in DEACCELERATION mode for too long, allowing the RPM’s to drop below 2,000 rpm. If the RPM is allowed to drop below 2,000 the engine dies it’s DEAD – NOTHING at all, and I than need to pull other and reset the ignition (on/off) 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 or spark, otherwise the engine would backfire when tying to restart after resetting the ignition...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 or 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. I’ve also 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 and has been like it for the last 3 tanks of fuel from different suppliers. My closest memory is that I recently washed the bike 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 started, not long after, or it was that around the same time that I do recall decelerating hard from red-line in low gear which felt strange at the time?

My thoughts;
1) My ThunderMax has a bug in the operating system and only fixes itself once reset...it’s not in the maps as I’ve also tried several older maps and the problem is still present?

2) My TSM accelerometer is faulty, may have got water in it and the kill switch is being activated under ‘G’ force...can anybody tell me if when this kill switch is activated does it kill power altogether or does it allow the engine to still run for safety reasons if fuel is injected?

3) My TPS sensor is faulty...but why does it only activate the fault under load?

4) My crank sensor is faulty...but if was the case why does the engine still run nicely once the faulty has been activated. It only dies if I have the throttle TPS lower than the RPM’s when in decell, till 2,000 rpm is reached and then it’s down and out.

5) My coil is faulty...it can’t handle the demand required when rev’d hand n fast...but why can the engine still be rev’d hard and fast after the fault has been activated?

6) My bike now has a gremlin and I need a bell?