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rough idle when cold

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rollo3076

Active Member
My 2011 eguc, with stage one and vance and hines power ovals and 33,000 miles, just started idling rough when cold,and will die if I don't hit the throttle to keep it going. It takes a few minutes to warm up and then idles pretty good, but I am getting the occasional spit and sputter on take off and some decel popping between shifts. I also noticed the red key light on the speedo is coming on too. Any ideas about what may be causing this and any way I can fix it, or does it sound like a problem the ext. warranty would cover? :(
 
Any other mods? are you running a fuel management system? with the stage1 and exhaust change you should probably be adding more fuel. Have you checked to see if you've thrown any codes?
 
Read some of the threads on fuel management systems, you probably need one. Getting the air/fuel correct will make her run much better and should cure your decel popping issue.
 
rollo3076 said:
My 2011 eguc, with stage one and vance and hines power ovals and 33,000 miles, just started idling rough when cold,and will die if I don't hit the throttle to keep it going. It takes a few minutes to warm up and then idles pretty good, but I am getting the occasional spit and sputter on take off and some decel popping between shifts. I also noticed the red key light on the speedo is coming on too. Any ideas about what may be causing this and any way I can fix it, or does it sound like a problem the ext. warranty would cover? :(
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Do you ever use Seafoam? Try it in a few tank fulls to clean the fuel system.

You may also be developing an intake leak. Use a unlit propane torch or some brake clean around intake manifold and see if there is any fluctuation in RPM.
 
dolt said:
Clean the IAC port on the throttle body.:s
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I agree with Dolt if your bike still has one of these on it. I think they stopped using this on the newer bikes, but can't remember when.

Harley Davidson Forums

As you can see in this thread (way late, like page 4 or more), I had trouble with my IAC on the '03 UC. Fiddled around trying to clean it with carb spray over and over. Finally replaced it and from then on no more periodic problems with these symptoms.

Cheers,

TQ
 
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I believe the IAC was eliminated in '08 when they went to FBW throttles. The TPS replaced it IIRC.
tourbox
 
Tourbox is correct; IAC valve was eliminated with TBW.

However, although the TBW bikes lack an IAC valve, they use the TBW instead; the maps still rely on the IAC valve concept. Internally the ECU translates the calculated IAC position values to throttle position ones.

The engine start process has 4 different stages:
1.cranking
2.crank to run
3.idle open loop
4.idle closed loop

The following is a description of the engine start process stages from someone more familiar with the process than I. You dealer should be able to connect and check for codes and will probably try to sell you a fuel management system in the process. I am not sure how the dealer connects to the ECM to correct such problems as I never go to the dealer but that is where to start.

If the RPM are below a given threshold (I think it is about 700 RPM) the stage is "cranking". In this stage the IAC position is controlled (for each temperature) by table "IAC crank steps" (plus some hidden offset X). In this stage, when the engine turns, the injectors open during a time controlled by table "Cranking fuel".

When the engine RPM go above such threshold, the stage changes to "crank to run". This stage lasts for about 1 second. During this stage the IAC position goes down exponentially to a value controlled by table "IAC warm up steps" (plus the same previous hidden offset X) from a value "IAC crank to run" steps higher. High "IAC crank to run" values will help RPM climb during this stage, whereas low values will aid in lowering the RPM.

When the "crank to run" stage ends, the "idle open loop" starts. This stage also lasts for about 1 second. In this stage the IAC position is controlled by table "IAC warm up steps" (plus the same previous hidden offset X). I call it "open loop" not because the O2 sensors are not used during it, but because the idle RPM are not controlled by the ECU and the table "Idle RPM" is ignored. The evolution of idle RPM in this stage is controlled by table "IAC warm up steps". Higher values will help RPM climb during this stage, whereas low values will aid in RPM going downhill.

Finally, after the "idle open loop" stage ends, the bike enters the "idle closed loop" (or "run") mode. In this stage all IAC tables are ignored and the ECU modifies the IAC position trying to maintain RPM at the desired idle value. This stage ends when the engine is stopped. After a few seconds inside this stage, the IAC position will eventually stabilize on its "correct" value for each temperature.
 
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