Buell EFI troubleshooting

BUELL EFI

TROUBLESHOOTING


We all know that EFI equipped ​Buell motorcycles don't always run properly.  Over the last few years, finding a Buell savvy technician with the proper diagnostic tools and abilities is also getting harder to find so many Buell owners find themselves trying to take matters into their own hands.  Needless to say, it's best to utilize proven tools and processes since replacing parts at random or because of an online "expert's" recommendation usually leads to wasted time and money.  Fortunately, you can perform extensive diagnostics and troubleshooting procedures using common tools, an Android device, and a BUELLtooth interface.  This means that diagnostics and repair of your Buell motorcycle is easier than you think.  This page is not only for use when a bike is running poorly or not at all, but it can also be used as a preventative measure or to make a bike that is running well, run even better.   

 

PREREQUISITES

 

Before beginning, you should ensure that some obvious, and maybe not so obvious conditions are met.  This includes, but is not limited to;

  • Clean and fresh PREMIUM grade fuel in the tank

 

  • Clean air filter

 

  • Static timing set correctly

  • A matched tune for your configuration installed on your ECM

 

  • View and record any active or store trouble codes.

 

*Note:  Don't replace a part just because a trouble code is associated with it.  Often, a Check Engine Light is caused by a sensor detecting a problem, not causing it.

 

COMMON ISSUES + FIXES

The following is a list of common things to do or look for as well as instances that have been experienced by others:

  • TPS Reset.  ​Lets just get this out of the way!  If you have replaced your ECM or loaded a new file this is something that needs to be done.  It's also not a bad idea to do this once a year or so on pre-2008 models.  However, it doesn't fix nearly as many problems as some people think it does.

  • Know your AFV and what it means.  This is often how you check the pulse of your motorcycle and decide your next course of action.  Without this information, you are operating blind.  You can also make changes to the AFV settings to help isolate issues. 

  • Intake leaks.  These bikes are notorious for having leaking intake seals, just like their HD cousins.  Due to the age of these bikes, its a good idea to replace the seals as a preventative measure.  The procedure isn't too difficult and the parts are inexpensive.  This is arguably the most common cause of "high AFV".  

  • Check your grounds.  So many problems are caused by bad grounds as these bike age.  There are several ground wires, splices, and mounting points.  Pay close attention to where these grounds mount to the frame and the bonding wires between the frame and engine.  A bad connection at any of these places will wreak havoc on your EFI system.  Bad grounds are known for causing a laundry list of trouble codes and/or intermittent issues with sensors.

  • Bike runs well at idle and low throttle, but lacks power at higher throttle settings, or cuts out completely.  On XB models this can be due to an improperly installed intake pipe which collapses at higher throttle settings. 

  • Fuel flow issues.   These can go unnoticed for a long time because the Buell ECM is able to compensate for low fuel pressure by increasing the Adaptive Fuel Value (AFV), up to a point.  If a fuel problem is suspected you should check this AFV setting immediately.  If it is significantly higher than 100 you should measure the fuel pressure which should be ~49 PSI.  Also, after a repair, the AFV must be reset back to 100.

  • Erratic or inaccurate engine temp.  This can be caused by a loose or defective Cylinder Head Temp Sensor (CLT), or a chafed sensor wire.  The ECM will adjust fuel delivery based on this data.  Using the live data page of Ecmdroid allows you to see sensor data in real-time as well as temperature compensation percentages associated with CLT and Inlet Temp Sensor (IAT).

  •  Inaccurate TPS reading caused by broken throttle shaft.  XB, X1 and S3 models have a common problem caused by a broken throttle shaft at one of the throttle plate mounting holes.  This causes a significant offset between the actual throttle position and what the TPS is reading.  Check for this before buying a TPS or other suspect sensor.  You may need to clean the area to perform inspection.     

Buell throttle plate mounting holes
Buell throttle plate mounting holes

TROUBLESHOOTING FLOW CHART

REVISION MOTO's Tutorials page has a list of guides that will help you perform the tasks listed in the chart below using Ecmdoid and a BUELLtooth device.  Refer to the applicable service manual for in-depth procedures, tolerances, wiring diagrams, etc.  These can be found on our Resources page. 

PERFORM DIAGNOSTICS

USING LIVE DATA

The Buell ECM makes adjustments based on data it receives from sensors located on the bike.  If the data from a sensor isn't accurate the bike won't run right, or maybe not at all.  There aren't very many sensors and viewing the data is easy, so the process of elimination doesn't take long.  Below is a screenshot of how you can set up your Data Channels Page of EcmDroid which will allow you to troubleshoot or narrow down a vast majority of EFI related problems WITHOUT spending money on parts or getting your hands dirty.  There are numerous other parameters that can be viewed but this is a good place to start.     

Troubleshoot screen shot.png

TPD (Throttle Position Degree)

 

On pre-2008 models, when the idle is adjusted to about 1100 RPM with engine fully warmed up, this should be about 5 degrees.  On 2008+ models it should be about 4 degrees.  When the throttle is moved it must change at a steady rate without any dead spots or spikes (see throttle shaft photos above).  At WOT it must read 85 degrees.  

AFV (Adaptive Fuel Value)

In factory closed loop operation, the ECM will make adjustments to the overall fuel delivery based on O2 sensor data.  At or near sea level this number should be close to 100.  If it is significantly higher than 100 it could be a sign of a fuel delivery problem so it would be a good idea to measure fuel pressure (on 1125 and 2010 XB models fuel pressure can be viewed on a data channel).  If this number is significantly lower than 100 you can isolate the problem by disabling closed loop which takes the O2 sensor out of the equation.  Remember that in closed loop operation, the ECM will use AFV to adjust for issues caused by mechanical problems.  It is also common for this to be at an unnecessarily low value, even when all sensors are working properly.  

IAT Corr (IAT Correction)

 

This shows you the percentage of fuel compensation the ECM is making based on the Intake Air Temp sensor.  Generally speaking, it should be more than 100 in cold air and close to 100 on warm days and while riding.  With factory settings the ECM will lower the IAT Corr (reducing fuel delivery) when the air temperature reading is abnormally high, which actually exasperates the problem.     

 

WUE (Warm Up Enrichment) and CLT (Engine Temp)

 

Warm Up Enrichment is based on engine temp or CLT (measured by the head temp on air cooled models, and coolant temp on 1125 models).  When the bike is completely cold the CLT should read ambient temperature.  As the bike warms up the CLT should increase and WUE should decrease until operating temperature is reached.  At this point the WUE should be close to 100.  If, for example, the head temp sensor on an XB is loose or defective the ECM will continue to enrich the fuel delivery unnecessarily which will be seen as a constantly high WUE number.  Also, the calibration or "learn" mode for AFV will not be active until a minimum CLT number is reached (on XB models the factory setting is 130).  Without accurate temp sensing the engine will never run correctly.