Warm-up rpm to high after first start-up. - Kawasaki Vulcan Forum : Vulcan Forums
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post #1 of 11 (permalink) Old 04-19-2010, 12:02 PM Thread Starter
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Warm-up rpm to high after first start-up.

I've had my bike for 2 years now. I always noticed the normal fast-idle that occurs when the engine is cold. The bike normally idles fast until about the second stop sign and then goes to normal idle speed. Recently, I have noticed a super-fast idle that occurs randomly only after a cold engine start-up. (Not necessarily cold outside, just cold for the engine. This has happened at 40F and 80F ambient temps.)

I do not have a tach, but I am guessing that if normal idle is around 1k and the normal fast-idle is around 1.8-2k, then this next level is in the 2.5-3k range. It is fast enough that if I am in 5th and downshift to 4th to slow down at a light, the bike actually speeds up slightly with out any input from the throttle. (I didn't think Toyota was affiliated with Kawasaki.)

My first thought was a sticking throttle like on old carburetors. So I reved the bike a couple times to break things loose, but this does not slow down the rpms.

I have found that I have to hold the clutch in, down shift all the way to 1st, come to a stop, let the clutch out just enough for it to grab a little and then pull it back in. Then the rpms drops back to normal warmed-up idle.

Has anyone else experienced this or do I have a ghost in yet another of my automotive computers? I don't think this is a fault that will kill me since I can always grab the clutch, but I would sure hate for my computer to suddenly decide I needed to be doing 90mph when a cage decides to pull out in front of me.

'07 VN900 Classic
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post #2 of 11 (permalink) Old 04-19-2010, 01:08 PM
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Yup, same thing happens to me. Sorta unnerving when you know the engine is warm and it shouldn't be revving that high. I haven't tried slipping the clutch like that, but i have noticed that it will drop to normal rpms after riding a little way.

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post #3 of 11 (permalink) Old 04-19-2010, 02:01 PM
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My fast idle works as it's supposed to. You must have the Kawyota model.

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post #4 of 11 (permalink) Old 04-20-2010, 05:56 AM
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I have high idle from time to time, but most of the time I'm just starting the bike, riding home/work and shutting off. Rarely do I go stop to stop. However, I've never really had much of a problem on my long distance, multi tank runs.
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post #5 of 11 (permalink) Old 04-20-2010, 06:50 AM
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Mine does the same thing. It's probably done it a total of 4 times. I didn't have any luck with the 1st gear/clutch thing you're talking about. After a couple minutes it just went back to normal.

The last time it did it, the first time I came to a stop (at a light) I shut it off and restarted it. It started back up at normal idle speed.

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post #6 of 11 (permalink) Old 04-20-2010, 11:07 AM Thread Starter
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Thanks for the input folks. At least I'm not the only one. I take it no one has come up with a fix? Or have we just decided its "normal". I guess that would suit me. Cause there's normal crazy and then there's crazy crazy. I try to fit into the first category with only short trips into the later! Maybe this idle thing is just normal crazy.

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post #7 of 11 (permalink) Old 10-08-2010, 10:17 PM
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Mine did it for the first time tonight. I wondered WTF? Got it to normal out (don't remember how). But it sure was wierd. Hope it does'nt start doing that all the time. Maybe make sure the throttle cables are working right and are lubed well?
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post #8 of 11 (permalink) Old 10-08-2010, 10:26 PM
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Could it be that the temp sensor in the bike is acting erratic, causing the ECU to respond? Just a guess.
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post #9 of 11 (permalink) Old 10-08-2010, 11:30 PM
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OKay, i read the service manual and there is this thing called "Inlet Air Temperature Sensor". Might be a good idea to check if its calibrated correctly. That might give a false input to the ECU causing erratic idling. Not saying this is the problem, but might be something to check to make sure.

Sorry no illustrations here, but you get the idea.
------------------------------------------------------------------------------------------------------------------------------------------------

Inlet Air Temperature Sensor (Service Code 13)
Inlet Air Temperature Sensor Removal/Installation
CAUTION
Never drop the sensor, especially on a hard surface.
Such a shock to the sensor can damage it.
• Remove the air cleaner housing (see Air Cleaner Housing
Removal).
• Remove the screw [A].
• Pull out the inlet air temperature sensor [B] out of the air
cleaner housing.
• Put the inlet air temperature sensor into the air cleaner
housing.
• Tighten:
Torque - Inlet Air Temperature Sensor Screw: 1.2 Nm (0.12
kgfm, 11 inlb)
Inlet Air Temperature Sensor Output Voltage
Inspection
NOTE
○Be sure the battery is fully charged.
• Remove the ECU (see ECU Removal). Do not disconnect
the ECU connectors.
• Connect a digital voltmeter to the ECU connector, using
needle adapter set.
Special Tool - Needle Adapter Set: 57001-1457
Inlet Air Temperature Sensor Output Voltage
Connections to ECU Connector
(Without Oxygen Sensor Equipped Models [A])
Meter (+) → Y lead (terminal 20)
Meter (–) → BR/BK lead (terminal 22)
(Oxygen Sensor Equipped Models [B])
Meter (+) → Y lead (terminal 26)
Meter (–) → BR/BK lead (terminal 28)
• Measure the sensor output voltage with the engine
stopped and the connector joined.
• Turn the ignition switch ON.
Output Voltage at ECU
Standard: About 2.25 ∼ 2.50 V at inlet air temperature
20C (68F)
NOTE
○The output voltage changes according to the inlet air
temperature.
• Turn the ignition switch OFF.
If the output voltage is out of the specified, check the ECU
for its ground, and power supply (see ECU Power Supply
Inspection). If the ground and power supply are good,
remove the air cleaner housing, check the wiring between
the ECU and the inlet air temperature sensor.
If the wiring is good, check the sensor resistance.
FUEL SYSTEM (DFI) 3-61
Inlet Air Temperature Sensor (Service Code 13)
Inlet Air Temperature Sensor Resistance
Inspection
•Remove the inlet air temperature sensor (see Inlet Air
Temperature Sensor Removal).
•Suspend the sensor [A] in a container of machine oil so
that the heat-sensitive portion is submerged.
•Suspend a thermometer [B] with the heat-sensitive portion
[C] located in almost the same depth with the sensor.
NOTE
○The sensor and thermometer must not touch the container
side or bottom.
•Place the container over a source of heat and gradually
raise the temperature of the oil while stirring the oil gently
for even temperature.
•Using a digital meter, measure the internal resistance
of the sensor across the terminals at the temperatures
shown in the table.
Inlet Air Temperature Sensor Resistance
Standard: 5.4 ∼ 6.6 kΩ at 0C (32F)
0.29 ∼ 0.39 kΩ at 80C (176F)
If themeasurement is out of the range, replace the sensor.
If the measurement is within the specified, replace the
ECU.

Last edited by krravi; 10-08-2010 at 11:42 PM.
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post #10 of 11 (permalink) Old 10-09-2010, 04:52 AM
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When I start from cold, I get the higher idle. I let the bike warm-up, which is a minute or so, until the idle drops down. Then, I ride.

It doesn't do this if the bike is warm. But, if cooled for over an hour, I think it does do it.

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