My 08 FXDC has developed a consistent issue with dying at idle. The first time you pull in the clutch after the bike is good and warm, say 10 minutes or so into a ride, the idle bottoms out and it dies. Cycle the ignition and restart and it's fine, can't make it do it again until the next ride. I'm assuming its the IAC, but it seems really odd that it will only do it once. Any ideas?

 

The idle control is very sensitive. That is why the idle is set at 1000 rpm or so. Could be the connection but if anyone has sprayed throttle body cleaner up into it, it's very possible the it is slow. Just spraying upward drives black soot up past O-ring into motor and it dries and sticks. Will do same to Throttle position sensor. Clean around the butter fly with a cotton cloth sprayed with carb or throttle body cleaner since the biggest part of the idle air is a preset opening there. The IAC get the rest. Key on and off to see how fast the pintle jumps out to cutoff all air and when keyed on back in.
You also have a MAP, Intake air temperature and of course the TPS.
Check your codes? All those parts are fairly cheap. All of them together is probably less the a couple hours at the dealer.

Crazy as it sounds, if I start in gear which of course lets the bike jump fwd will result in a 200-300 higher idle to my next restart. Never have figured out why it gets lost...Do you have a tuner. Is enough miles on bike that it could be plugs?.

 

Not throwing any codes, which is what had me thinking the IAC was losing counts. The bike is an 08 with 21,000 miles. I bought it last year with 13,000 miles and replaced the plugs then.

No tuner - XIEDs with Screamin Eagle air cleaner.

 

Don't use carb cleaner or throttlebody aerosol cleaner to clean the IAC. Use a Mass Airflow cleaner aerosol.

 

Not as simple as just cleaning the IAC. The first time the issue popped up that did help, but it's come back and become consistent to the point that the bike dies at the same red light when I leave my office. At this point I'm pretty certain I need to just replace the IAC, I'm just intrigued by how regular it occurs and that it will only happen once in a ride.

 

It's just probably slow and the computer can catch it most of the time. It's only a $50 part. If you've tried to clean it, I would replace it. They rarely would ever be a need to truly clean one. Usually just around butterfly if it gets sticky. And usually only then when people cannot resist the temptation of putting other things in the fuel tank other then gasoline.

 

Up the idle speed.

 

His model is Fuel Injected and only the dealer or a service center with the Harley scan tool can modify idle speed.

To add my 2 cents I think maybe your Throttle Position Sensor may be at fault. The computer may not know when you close the throttle so it doesn't try to adjust the IAC that first time. When you start the engine the computer runs in an open loop and preset for cold start and fast idle. It bumps the IAC a bit and ignores the throttle. That's why your problem only shows up on the first stop light. Remember your TPS spends most of it's life at closed throttle and it's just a variable resistor. So just like your old stereo volume control, it can develop a dirty spot where the reading is unreliable. Remember the scratchy volume control on that stereo? Since the bike does go to fast idle then adjusts idle later I doubt the IAC is at fault or sticking.

One cheap and easy thing to try is to remove the air cleaner to expose the TPS electrical connector. Push the tab and pull it loose. Then use some Electrical Contact cleaner ONLY to clean both male and female contacts. Mate and unplug the connector a couple of times and finally plug it back in. That won't address the problem if the TPS is in fact bad but a common problem with HD FI are those electrical contacts get dirty and cause all kinds of problems.

CRC QD Electrical Contact cleaner at Home Depot works very well and is safe around plastic.

 

Your Throttle Position Sensor use to be an easy check with a Volt/OHM resistance meter. I have a 2008 Dyna service and electrical service manual for the checks but they no longer list a simple check other then volts using their equipment. However, you should see it change with a meter. Interesting but the IAT,ET and TP provide info to the ECM to fine tune spart and fuel. The VSS (vehicle speed sensor) is used as an input for idle speed control.

Just how does that XIEDs work. I would consider it a tuner?

Hay OLDenough2, what makes you think Mass Airflow cleaner aerosol is not going to drive liquid dissolved crud up past that O-ring in the IAC motor-resolver?. That port that the V shaped pintle opens is huge. You can see the mouth opening and the V of the pintle to actually see if it was fouled.

 

The Mass Air Flow Cleaner will evaporate much quicker and will dislodge any accumulated dirt without leaving any deposit behind.