Hi guys. I have a 2007 Fatboy with about 25K on the clock. I have an SE intake, V&H BSS and have my bike tuned with a fuel map from the SERT calibration number 159AE003 (SERT install disc 32117-01J). There are no internal modifications to the bike and the fuel map criteria match my bikes running condition.

I recently have begun to notice a few things about my bike and the way it runs it has definitely been about a month or two since the symptoms began to manifest, but it was barely noticable at first. Seems to be getting worse.

1: She seems to have NO get up and go in gear right after part throttle all the way up to WOT. So if I take off from a stop light in first after the clutch is fully engaged, if I go wide open throttle it STUMBLES all over itself. This is also true in any other gear. at Wide Open Throttle it feels like she doesnt want to accelerate at all.

2: Having a harder time starting lately; definitely an extended crank situation. Used to be a second tops for her to fire up, now its more like 2-3 seconds.

3: Idle sucks! I know that it is most likely a failing or clogged Idle Air Control valve so not too concerned about it, but could that cause my bike to run like ***?

I have an appointment to take her in to OC Harley this Saturday for a few things namely throttle cable adjustment, clutch adjustment, neck bearing adjustment, and diagnosis of this ride-ability issue. I THANKFULLY got the 3 year warranty for my bike when I purchased it so I hope they figure it out.

As it stands right now, I DO NOT have a check engine light on. this leads me to believe that there are a few scenarios that seem likely.

1: My MAP (manifold absolute pressure) sensor is on the fritz and sending inaccurate information to my ECU. Likely the wiring harness is ok as no codes have set. If there was an open or short in the harness, there would probably be a code set.

2: TPS (throttle position sensor) is inaccurate and the ECM is trying to adjust to the condition it sees

3: 02 sensors are failing and sending bad data to the ECU creating a poor fuel mixture (either rich or lean, most likely rich)

4: The ignition control module and/or coil packs are malfunctioning and sending poor spark to the plugs. Plugs are fairly new and gapped to the factory specs.

I dont hear any abnormal noises either at idle, reving in neutral or under load. Oil changes every 4-5k miles using OEM filter, Mobile 1 V-Twin in all 3 holes, and regular fluid checks. I dont smell any raw fuel in the oil so I dont believe that there is any cylinder wash occurring.

So my fellow Harley-Davidson riders, what could be going on with my bike?

 

The IAC could be stuck?

Developed a vacuum leak?

Weak battery or poor ground?

 

might be time to clean the air filter ...

 

currently the bike sports a K&N air filter thats been recently (about) 2k miles ago. washed, dried and re-oiled.

 

Whatever you find out - please remember to post it back here for future reference

 

Had similar symptons on an 05. Turned out to be the TPS. It threw a code though.

 

Well I have an update for everyone. The bike is not fixed yet BUT I do have some very good news. I FOUND MY BIKE AGAIN!

Clarification:
I just noticed today starting the bike up that the check engine light will illuminate a few seconds after startup. It will stay on for about 4-5 seconds then go off. After I noticed this going on, I was riding my bike (unless its raining its my daily ride) and had to juice the gas to make a pass. Now the last few weeks (likely a month) I have been used to having to go wide open throttle just to accelerate with any type of momentum around a car. But TONIGHT after I noticed my check engine light come on then go off, I twisted the throttle and good GOD did she scoot like a raped ape!

Haha I looked down and asked "Where the hell have YOU been the last month?!"

I have come to the conclusion that my bike's ECU has gone into a closed loop bypass mode. It is seeing something wrong with one of its feedback signals and had defaulted to open loop operation. In this case, it could LIKELY only be failed oxygen sensors!

It makes sense; bike has been using alot more gas, running like crap and stumbling all over itself. Two words: FUEL TRIM

The ECU will make two types of fuel trim corrections: short term fuel trim and long term fuel trim. short term is just that; minor fuel corrections to keep the air/fuel ratio at the programmed mixture for the current situation it sees. if the short term fuel trim adjusts far enough in one direction for a long enough duration (rich or lean) then the long term fuel trim (what the ECU sets base fuel mixture at) will adjust rich or lean.

Most ECUs are programmed with a fail safe logic that will trip a constant check engine light when it sees a hard fault like an engine speed sensor no longer generating a signal or an engine temp sensor thats either shorted or open.

In THIS case, I think that the light coming on and turning off is indicating that one or BOTH of my air/fuel ratio sensors (oxygen sensors) has adjusted long term fuel trim to a point that the ECU KNOWS that there is no way that it could be correct. When it looks at all the other data being input to it (such as load, throttle position, engine temp and speed) it KNOWS something aint right.

So in MY diagnostic opinion, i believe that the ECU knows the oxygen sensors are lying to it and its no longer paying attention to it for feedback information and running on open loop. My oxygen sensors, it seems, are dead.

I still definitely plan to take it back to Harley for diagnosis and repair, but dealing with cars all day long this seems like the logical explanation for what the hell has been going on with my bike! Ill let everyone know what happens at the dealer and their diagnosis.