Transient high idle problem
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HDF Community Team
Joined: Nov 2012
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From: USA
Transient high idle problem
04 Road King Classic, injected, has cruise control.
It's only happened once, but I'd rather it never happen at all.
About an hour into a ride last week the engine failed to return to idle. It held a high idle of about 2,000 rpm for about 30 seconds. Attempts to force the throttle close gave no results, and felt perfectly normal and solid. Rolling the throttle open and letting it snap shut was just as unsuccessful. After about 30 seconds the engine returned to proper idle on its own. I continued the ride without incident. I have not been out on it since, though that's because of weather, not fear of this problem.
This was on a cool day, and it was the first ride in about 9 months. The battery had been out of the bike.
No signs of any obstruction in the throttle wheel, no bind in the cables, no signs of anything in the throttle body itself. Vacuum port cap is present and in fine shape.
My suspicion is that the idle air controller opened, increasing the idle speed. It was cool weather, and I was puttering along on back roads, but the temperature sensor should not have thought the engine was cold.
I've also wondered about the cruise control. I'd been using it that ride, but not at that point in the ride. Perhaps I did hit it, but the brakes should have kicked it off. I did have a problem working on the bike once with the actuator not properly letting the tape out.
I'd be curious about what some of you think. If someone has had this problem, I'd be especially curious to hear what you found to be the cause and fix.
It's only happened once, but I'd rather it never happen at all.
About an hour into a ride last week the engine failed to return to idle. It held a high idle of about 2,000 rpm for about 30 seconds. Attempts to force the throttle close gave no results, and felt perfectly normal and solid. Rolling the throttle open and letting it snap shut was just as unsuccessful. After about 30 seconds the engine returned to proper idle on its own. I continued the ride without incident. I have not been out on it since, though that's because of weather, not fear of this problem.
This was on a cool day, and it was the first ride in about 9 months. The battery had been out of the bike.
No signs of any obstruction in the throttle wheel, no bind in the cables, no signs of anything in the throttle body itself. Vacuum port cap is present and in fine shape.
My suspicion is that the idle air controller opened, increasing the idle speed. It was cool weather, and I was puttering along on back roads, but the temperature sensor should not have thought the engine was cold.
I've also wondered about the cruise control. I'd been using it that ride, but not at that point in the ride. Perhaps I did hit it, but the brakes should have kicked it off. I did have a problem working on the bike once with the actuator not properly letting the tape out.
I'd be curious about what some of you think. If someone has had this problem, I'd be especially curious to hear what you found to be the cause and fix.
Road Master
Joined: Jun 2005
Posts: 1,053
Likes: 39
From: Central Florida
I had a similar issue on a Fuel Injected Evo.. was the throttle position sensor.. Not sure if that would still apply to a twin cam motor or not. But when it happened I had to shut the bike off and on and it came back to normal. Freaks you out though.
Stellar HDF Member
Joined: Jan 2009
Posts: 2,578
Likes: 463
From: On a Lake, not far from the Gulf
First thing to do is to check for historic trouble codes. When you were trying to get it to idle down was the idle speed lever closing completely? If so it may be the TPS. If not then what you suspect is more likely. Try cleaning the IAC. Also make sure you synch the ECM with the IAC. There is a key ON/OFF series that is explained in the manual.
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HDF Community Team
Joined: Nov 2012
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From: USA
Ah, It was carrying two historic codes, P1351 and P1354. Interesting, since according to the light check, it had no stored codes. Only when I went and did the diagnostics did it reveal it was storing these two. Seemed a little balky starting, but it tripped no more codes in the few minutes it sat there running. Now that I think about it, I probably tripped those months ago doing the cam chain tensioners. I'm almost certain I used the starter to turn the engine a few times, with the coils disconnected.
I don't know what you mean by idle speed lever. If you mean the throttle plate, I don't know as I was riding at the time. Throttle grip felt ok, but that's rather meaningless.
I'm trying to find in the manual about where when and how to sync the ECM with the iac. Some things are remarkably obscured. I'll find it eventually.
I don't know what you mean by idle speed lever. If you mean the throttle plate, I don't know as I was riding at the time. Throttle grip felt ok, but that's rather meaningless.
I'm trying to find in the manual about where when and how to sync the ECM with the iac. Some things are remarkably obscured. I'll find it eventually.
Last edited by foxtrapper; Mar 19, 2014 at 05:38 PM.
Stellar HDF Member
Joined: Jan 2009
Posts: 2,578
Likes: 463
From: On a Lake, not far from the Gulf
The idle speed lever it the lever that the IAC activates. It is connected to the right side of the throttle body. The ECM synch instructions are probably in the fuel tank section in the service manual. I could tell you what is is on mine but it may be different for the Delphi system.
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