Help troubleshooting low idle issue - please read and contribute
Seasoned HDF Member
Joined: Mar 2010
Posts: 38,586
Likes: 6,435
From: Honah Lee
Thanks FBRR. Some good info. Shortly I plan on doing the leaking injector test (5 times on/off key to see if any fuel pools in throttle body. If it does I am hoping the injectors I got with the throttle body above will fit. I know I have a little run on sometimes, a loud pop on about ever 3rd or forth start and at least a 75 rpm hunt at idle. Son says it's missing but it runs great and I think is just a little uneven with a a little leak in the injector at 40K. Does your's ever backfire in the exhaust on start up? It's only done it once in the intake but it was 35 degrees late at night leaving work.
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Road Master
Joined: Feb 2010
Posts: 804
Likes: 1
From: 415
Interesting detailed discussion above.
Update on my story: I bought a new IAC and a new TPS. I installed both (with the main fuse pulled) and then after installation I re-initialized the TMAX with a 3x30-second on/off cycle.
When I went to start the bike for the first time to run an IAC-stop auto-calibration all hell broke loose. There were repeating huge "smack" sounds coming from the air-cleaner area. (IAC going nuts?) The engine was racing (while cold). It stalled twice. It would not hold a proper idle, even as the IAC-auto process was running. I had to stop the madness and shut the engine down. I was worried at this point.
After shutdown I did a quick 7 on/off cycles. Then I did the 3x30-second TMAX initialization. Then I let the bike cool down. (Put away my tools).
When the bike was cool again I gave it a second try.... it worked, and sounded smooth. I think I made progress in the idle issue. I ran IAC-auto and it tracked well. My adjusted IAC stops are now in the 20 range.
So... I think even if you are running a T-Max you may need to do the 7 on/off quick cycles to get the HD ecm initialized after swapping these components. I don't know for sure, but it worked for me. I am also considering myself lucky that my new IAC still works after that first session. It sounded like it was trying to self-destruct.
Update on my story: I bought a new IAC and a new TPS. I installed both (with the main fuse pulled) and then after installation I re-initialized the TMAX with a 3x30-second on/off cycle.
When I went to start the bike for the first time to run an IAC-stop auto-calibration all hell broke loose. There were repeating huge "smack" sounds coming from the air-cleaner area. (IAC going nuts?) The engine was racing (while cold). It stalled twice. It would not hold a proper idle, even as the IAC-auto process was running. I had to stop the madness and shut the engine down. I was worried at this point.
After shutdown I did a quick 7 on/off cycles. Then I did the 3x30-second TMAX initialization. Then I let the bike cool down. (Put away my tools).
When the bike was cool again I gave it a second try.... it worked, and sounded smooth. I think I made progress in the idle issue. I ran IAC-auto and it tracked well. My adjusted IAC stops are now in the 20 range.
So... I think even if you are running a T-Max you may need to do the 7 on/off quick cycles to get the HD ecm initialized after swapping these components. I don't know for sure, but it worked for me. I am also considering myself lucky that my new IAC still works after that first session. It sounded like it was trying to self-destruct.
Ultimate HDF Member
Joined: Mar 2007
Posts: 7,465
Likes: 15
From: Corona, Ca
hey macnab hows the bike running since iac and tps replacement?
I just finished my 106 build and while I had the throttle body off I removed the iac, cleaned it up and got the bike back together and the idle is worse.
I just did the 7 quick on/off cycles to recalibrate it and she started 3 times in a row without the low idle/stalling on start up.
if she acts up again tomorrow ill pick up a new iac while im at the dealer tomorrow night.
I just finished my 106 build and while I had the throttle body off I removed the iac, cleaned it up and got the bike back together and the idle is worse.
I just did the 7 quick on/off cycles to recalibrate it and she started 3 times in a row without the low idle/stalling on start up.
if she acts up again tomorrow ill pick up a new iac while im at the dealer tomorrow night.
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Road Master
Joined: Feb 2010
Posts: 804
Likes: 1
From: 415
hey macnab hows the bike running since iac and tps replacement?
I just finished my 106 build and while I had the throttle body off I removed the iac, cleaned it up and got the bike back together and the idle is worse.
I just did the 7 quick on/off cycles to recalibrate it and she started 3 times in a row without the low idle/stalling on start up.
if she acts up again tomorrow ill pick up a new iac while im at the dealer tomorrow night.
I just finished my 106 build and while I had the throttle body off I removed the iac, cleaned it up and got the bike back together and the idle is worse.
I just did the 7 quick on/off cycles to recalibrate it and she started 3 times in a row without the low idle/stalling on start up.
if she acts up again tomorrow ill pick up a new iac while im at the dealer tomorrow night.
The idle still is not as even as I want it. Sometimes it just idles too slowly. It also coughs off the line occasionally.
I bought new hose for inside the gas tank, but have not yet installed it. That's another often-mentioned reason. I sometimes wonder if there's something wrong with one of the 25-degree injectors I got off ebay. I have not plugged in my PC to the thundermax in a while, but there are no errors showing on the speedo.
Ultimate HDF Member
Joined: Mar 2007
Posts: 7,465
Likes: 15
From: Corona, Ca
so she starts right up this morning, but as soon as I pull her out in the street she wouldn't run again....
this is starting to **** me off, I have no CEL so no codes....
its acts like the battery is low and the idle is around 600 rpm until it stalls out...
this is starting to **** me off, I have no CEL so no codes....
its acts like the battery is low and the idle is around 600 rpm until it stalls out...
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Road Master
Joined: Feb 2010
Posts: 804
Likes: 1
From: 415
Not a bad idea. I can save my current map too, and then restore it afterward. The bike did cough off the line before switching injectors.
That's an easy one to try.
Don't know how to help. That sucks. I've been able to get a guy on the phone at zippers before. They will want to see your map and some log files if you can get them.
Don't know how to help. That sucks. I've been able to get a guy on the phone at zippers before. They will want to see your map and some log files if you can get them.
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Thread Starter
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Road Master
Joined: Feb 2010
Posts: 804
Likes: 1
From: 415
Yes essentially the issue is solved. I did all the little things mentioned. Recently I flashed the ECM firmware (zipper's thundermax), changed all three fluids, and idle has been good since.