The TPS tell the computer where the throttle blade angle is. You can ohm the TPS to see if it is open. Check around the butter fly and see if it has varnish build up in the bore of the throttle body. You get some air around it and if there is varnish it will block that air. Then when you go back to idle the IAC dose not know you are not geting that air so you get a low idle till the IAC moves to make up for the lost air. I used to teach automotive computers anf fuel injection for years and this was common. Use O2 safe cleaner on a rage and wipe it clean. You can also get a varnish build up in the IAC passage.

 

I'm going with "Low fuel pressure"

 

Because the pump regulates at a constant rate freeway speeds would be an issue not idle.

 

I had the same problem. New plugs and ran some sea foam in with the gas and withing 30 minutes it was back to normal. I am now a firm believer in sea foam.

 

My o7 FXD was the same and tried seafoam cleaner and know frequently kuse the additive to my fuel.

 

Ripsaw and everyone, thanks for the help.

Responses:

You leave out some very important details. Miles on I assume the 2006 Dyna.

Yes - 06 dyna. 25k miles


1.Are we talking a stock bike or all kind on mods and piggyback tuners? Forget my help

Has a Thundermax installed. I can't forget your help though. TMax was present before the idle issue arose.

Couple notes:
I switched to 25-degree injectors from 8-degree (stock) ones. I bought the injectors off ebay. They looked new and included new o-rings. When I put the new injectors in I loaded a new map to go with it. I do not recall the idle issue happening immediately after that, the idle issue comes up later on, but these were things that were changed relatively recently.



2. How long has this been going on and has bike been stored. Short time and stored. Replace all gas.

I guess problem present about 30 days now. Bike has not been stored at all, been ridden all the time.

3.Maybe a load of fuel stabilizer or crud. First thing to go if the filter is crudded up is idle since ECM can not keep control of idle due to low fuel injector pressure. Check is rather complicated with out gages and connectors. Doing your own work and crud in tank. Just replace filter.

Good suggestion. I will check/replace fuel filter. I have not done this yet. I did buy a 16oz bottle of sea foam and poured about 1/3 of it into the mostly-full tank.


4. Once you crudely spray tons of carb cleaner crudely into throttle body or IAC passage way it washes black carbon deposits up into IAC linear motor past o-rings or TPS and in just a few days both are trashed due to sticking.

Agreed it was the wrong move, but it wasn't "tons" and I don't believe much made it down the intake. I used a rag to catch the residue. The issue was present before I sprayed the carb cleaner the first time, and it hasn't gotten any worse.

5. IAC is easy check key on and off and watch it after you read how it works and a little spray down passage way and see it come out hole at top just behind throttle plate.It is an air way--nothing more.

I verified that the IAC motor is moving last night by cycling the ignition switches and watching with a drop light, it appears to move smoothly. I also used proper MAF spray last night into the IAC (with catch rag on the other side of the throttle plate) and it's coming out pretty clean on the other side.

5. TPS is easy check with service manual and resistance meter.

I have to check manual to get clarification on where to measure the TPS voltage. I can do that this evening


6.Throttle plate stop screw is just that and should never be adjusted. With throttle plate shut it should completely shut off throttle body. The stop screw keeps plate from digging into bore but a little carbon crude should stick plate. If it ever does, open butterfly and reach in with a sprayed cloth and wipe off and the lip of the plate. Has nothing to due with idle, just sticking.

Acknowledged. Have not touched idle screw. Things look pretty clean inside intake behind and around the throttle plate.

7.Replace spark plugs just for good measure.

On the list, not done yet.

8.Ever pressure wash it or use tons of cleaners on it. Could be a bad electrical pin connector on IAC or TPS or the IAT (intake air sensor)

No I don't wash it with water. I use Gibbs mainly. Used to use wd40, but I don't like what it does to rubber.

9.Does your battery have 12.6volts DC

I'll verify when I check TPS voltage. The battery lives on a tender at night, and always cranks strong in the morning, so I think the batter is OK. Worth checking. [My car is another story, battery has gone dead twice from non-use.]

Any of that help?

Absolutely it is, thanks for taking the time and energy to post it. I haven't worked through all your suggestions yet but I plan to and will post progress.

Thanks

 

Did you look to see if the TMax has any diagnostic codes when you go into the TMCC? The TMax doesn't like an even slightly weak battery and will display a battery issue under diagnostics.

 

Hope I do not offend but just wanted to add hopeful some clarification to my thoughts.

4. Once you crudely spray tons of carb cleaner crudely into throttle body or IAC passage way it washes black carbon deposits up into IAC linear motor past o-rings or TPS and in just a few days both are trashed due to sticking.

Agreed it was the wrong move, but it wasn't "tons" and I don't believe much made it down the intake. I used a rag to catch the residue. The issue was present before I sprayed the carb cleaner the first time, and it hasn't gotten any worse.

Let me go into a little more depth here. The don't believe much made it down the intake is not the problem I have seen. What I have seen happen is when you tear the IAC and TPS apart you will see that on the IAC as you go up the shaft from the little v-shaped pintle valve it goes thru a o-ring seal and then what appears to be a linear motor solenoid with a sensor for position. The TPS is similar shaft arrangement but it is basically a rheostat switch and I think a full off idle position and a full on wot position. By spraying too much especially if there is some crud on throttle plate and or throttle body bore it washes this down those shafts right past the loose seals into the inside of the switch controls and screws good switches up.

On fuel pump pressure. The pressure is always the same since the pump puts out way more then the the engine needs. There is a pressure relief in tank that always bleeds off even at wot. The pump runs all the time once gas motor starts. The pump can fail if the armature brush (runs in the fuel flow believe it or not)wears out in the electric motor but motor would not even start if this happens. However I doubt the impeller can fail. However if the filter gets stopped up enough to restrict gas the normal around 55 lb running pressure will drop and it does not take much and then the ECM cannot catch the idle fast enough when you come off speed. With carbs lack of fuel pressure affect top speed. With FI cars and bikes it affects idle. Normal flow is thru filter sock thru pump to fuel filter then thru pressure relief valve all in tank. A rubbed thru or crack between the pump to the fuel filter would affect idle thru low pressure.

I think askbob post is mixing carb and FI butter fly closed position together. With a FI bike at idle the butterfly is completely shut. If by chance someone turns the fixed factor set stop screw and opens the butterfly at idle it will actually increase idle (it would just be like cracking throttle) however shortly the ecm will catch it and correct set rpm with the IAC pintle valve. However when you cut off these 1000 rpm idle bikes the pintle valve jumps in and shuts off all air so you do not get run-on. If you have some of idle controlled by butterfly you may get run on.

 

I have similar problem, idle drops at a light, sometimes stall the engine, every restart back to normal. I have cleaned throttle butterfly, iac motor, zero throttle in PCV, still does it randomly. I have found a TSB TT-410 about re-flashing ecu, not sure about it. People talk about this in the touring forum as well https://www.hdforums.com/forum/touri...le-issues.html and here http://www.hdtalking.com/dyna_models...e_changes.html
I think it has something to do with IAC position, can't find the right place sometimes, it is annoying.

 

Mine died yesterday for the first time as I was coming to a stop...I will be going thru everything this weekend tps, iac, and check the filter & fuel line.