Ok, my Harley is a 2015 Dyna Wide glide. Stage 1 with V&H FP3 tuner. First things first. 6 months ago I removed the IAC (idle air control) to install a manual idle control, which I loved. Now, im about to do a stage 2 and Andrews cam's said they wouldn recommend using that. So, I went to my Harley dealership this morning and bought a new IAC for my bike. (Because the original got lost) I installed the new IAC without problems. Buttoned everything up and Fired her up! Right off the Bat my idle went straight to 4000rpm! But only for 3 seconds, then slowly dropped right into the startup range it should be running. I let it fully warm up and it finished at 1050 rpm idle. I shut her off and tried starting her up again. She fired right off and went straight to 3500rpm for the same 3 seconds. Every start I do now, this very high idle pops up for 3 seconds. I cant figure out why? Has anyone experienced this before? Im at wits end. Thanks for anything you can throw at me to remedy my situation.

 

Just a complete shot in the dark, but could it possible be a faulty IAC? If the install went smooth and it didn't surge with the original IAC, my guess would be a faulty part.

Just my .02

 

I thought about that. But after riding for 6 months with a manual idle control installed, I could NEVER set my warm up rpm where the computer wants it and idle down like its needs to. So I would check my FP3 on my phone and it was always showing codes for too high of idle at start up or just the opposite too low. So, im going to go in tomorrow and clear all the codes that have popped up. Maybe doing that will make her act right? Im really hoping my IAC isn't bad.

 

1. Ensure no intake leaks
2. Confirm correct throttle body butterfly opening and/or throttle cable adjustment (should be a procedure for adjusting base idle in the service manual)
3. Observe startup behavior.
If that doesn't fix it....
Remove FP3, return to stock tune, and observe behavior.
If that fixes it, the problem is likely the FP3/tune.

Additional thoughts...
Does the IAC and ECU have a learn or calibrate requirement? It's a stepper motor and may need mated to the ECU so it can home properly.
Does the FP3 have IAC control/setting fields or table? You may need to enable IAC or set parameters.

 

That was the other possibility I was thinking about, but he didn't mention any type of rpm surge before that. Still something to consider and check for.

 

Probably nothing wrong mecahanically.. You can try resetting the ECM by unplugging the fuse but the ECM has bee trying to adjust the non exisistant IAC for some time and it's been railing internal values. It needs to relearn the correct ones with a functioning IAC. Don't know abut the FP3 but some systems have a default initial setting for the IAC also.

 

IAC may be getting a higher voltage input than what is required.


Not sure if the FP3 can alter cold start decay, start up enrichment etc like a PV but a setting may be buggered there too.

 

Just a note.. The ECM does not change voltage to set the idle air. The IAC is a stepper motor which is driven by the ECM.

https://en.wikipedia.org/wiki/Stepper_motor

 

Thanks to all of your inputs on the possibilities to my problem. I tried Max Head flow idea about resetting the ECM. After doing that, everything is back to normal. Thanks again y'all for saving me a from a big future Headache.

 

FWIW, there's a reset procedure to reinitialize / resynch the ECM / IAC. It will set the IAC to it's most closed position and then record that position in the ECM.


Set the run / stop switch to run and cycle the ignition switch to Ign for 30 seconds on, 30 seconds off, repeat 3 times.