For the past few months I’ve been having an idling problem on my 02 EFI Fatboy. After about 20 minutes of hard throttle, the engine would stumble and idle at roughly 500 rpms when coming to a stop and pulling in the clutch. I could work the throttle and keep the bike running, then after a couple minutes the engine would idle properly on its own at 1000 rpms. Eliminating the Crank Position Sensor and Speed Density Indicator as the cause of the problem I determined that the problem may be due to a faulty or dirty Idle Air Control Valve (IAC). The HD Electrical Diagnostic Manual states that the Idle (IAC) resets itself each time the ignition is cycled. As a test, I turned the engine off then restarted it during one of the low idling periods. The bike started up and idled correctly confirming my suspicion that the problem was most likely the (IAC).

Since the bike is 12 years old I decided the replace all 5 EFI sensors located under the fuel tank:

Idle Air Control Valve
Throttle Position Sensor
Intake Air temp Sensor
Manifold Air Pressure Sensor
Engine temp Sensor

The sensors are attached with very small screws and Harley applies a strong thread locking compound to the threads. Additionally the Throttle Body is attached to the Intake Manifold with two screws that cannot be accessed while the unit is mounted on the bike. The HD Service Manual states; to replace any of the sensors, the Intake Manifold and Throttle Body must be removed from the bike and while on a bench, Heat must be applied to the screws to loosen the thread locking compound. Thinking there must be an easier method, I decided to try and replace the sensors with the Intake Manifold and Throttle Body attached to the bike. The fuel tank had to be removed of-course. I got lucky and was able to break all the screws free without damaging them. There is little room around the Throttle Body requiring patience and finesse to change the components.

The plunger tip of the (IAC) is visible when looking into the throttle body after the air cleaner assembly is removed. Mine looked clean, however after removing the (IAC) I could see that the plunger shaft was severely coated with dirt and grime which could have impeded it’s operation.

Note: The HD Service Manual states that the screws for the sensors are to be discarded and new screws utilized. I learned after the fact that all the screws have separate stock numbers and are not included when purchasing new sensors.

My most difficult challenge was replacing the Engine Temp Sensor. The sensor is recessed in a cavity preventing the use of a wrench. A standard size socket will not clear the electrical connection housing on the sensor and a deep well socket is to long to fit between the fins of the jugs. I ended up cutting a half inch off of a thin wall, deep well socket which then allowed enough clearance to remove and replace the sensor.

Summery: All the sensors located under the tank can in-fact be replaced without removing the Intake Manifold and Throttle Body.

 

Thanks for the info. You can apply a soldering iron to the screw heads to help with the thread locker, too, but only with small screws.

 

Did replacing all the sensors fix your problem?

 

I was able to R&R the IAC and TPS by just raising up the back of the tank, so if that's all you have to do, no need to remove the tank. Just an FYI.

 

Opencaliber,

Yes, replacing the Idle Air Control Valve corrected my idling problem. I replaced the other sensors simply because of their age. It's a 12 year old bike and I'm a firm believer of preventative maintenance. Additionally, I'm riding in the Philippines without dealership or any other sort of mechanical support. When we ride, we need to be certain that our equipment will get us home.