LCV issue - Road Star Warrior Forum : Yamaha Star Warrior Forums

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Old 10-27-2012, 12:42 PM   #1 (permalink)
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Default LCV issue

I recently bought a 2003 warrior. When i bought it the LCV was not functioning, so i replaced it. The new LCV opens and allows the bike to high idle when cold, but once it warms up, the idle jumps between 900 and 1400 rpms. Do i have a bad replacement LCV? how can i check its function? I understand that the LCV works off the oil temp sensor. could that be the problem? how do i test that? I previous owner did not have the tps recall done. could that cause it?

Thanks for your help.
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Old 10-27-2012, 02:00 PM   #2 (permalink)
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Took mine off a couple years back and never looked back. I crack the throttle on startup and hold it there for about a minute or so, then drive off.. taking it easy until it gets nice and warm.
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Old 10-27-2012, 02:43 PM   #3 (permalink)
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Just unplug the lcv and see if your idle acts normally. If your idle does go back to normal, just get rid of the lcv as I and others have done.
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Old 10-27-2012, 03:16 PM   #4 (permalink)
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No LCV here. Same as 4U and Matt. Never a problem.
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Old 10-28-2012, 12:32 PM   #5 (permalink)
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I would like it to function if possible. Any other thoughts?
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Old 10-28-2012, 01:34 PM   #6 (permalink)
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Reference a service manual for diagnostics.
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Old 10-28-2012, 01:52 PM   #7 (permalink)
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Quote:
Originally Posted by hyper1685 View Post
I would like it to function if possible. Any other thoughts?
If you want to completely rule out any issue with the new LCV i would suggest plugging both the TB's (throttle body) connections. You can leave the electrical connection as is as well as the filtered inlet.

By isolating the TB's connection will rule out any defective cross connection within the valve body. If your erratic idle persists you'll know the issue isn't the LCV and you can carry on with some logical trouble shooting ... good luck
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Old 10-28-2012, 02:19 PM   #8 (permalink)
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Thanks Alan,

I know it is an issue with the LCV because I can turn the idle adjustment screw all the way out (cold or Warm) and the bike does not die. I LCV is still letting in air once the bike is warmed up. If I plug the LCV intake hose, the bike runs like it did with original LCV installed. Does anybody know how to test the LCV and related sensors that control the LCV? as far as i know, the only sensor that controls the LCV is the oil temp sensor. Is that correct?

Thanks
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Old 10-28-2012, 04:10 PM   #9 (permalink)
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Originally Posted by hyper1685 View Post
Thanks Alan,

I know it is an issue with the LCV because I can turn the idle adjustment screw all the way out (cold or Warm) and the bike does not die. I LCV is still letting in air once the bike is warmed up. If I plug the LCV intake hose, the bike runs like it did with original LCV installed. Does anybody know how to test the LCV and related sensors that control the LCV? as far as i know, the only sensor that controls the LCV is the oil temp sensor. Is that correct?

Thanks
I'm a bit confused by your 2nd response but you've clearly stated that by plugging the LCV inlet that the bike idles normally when HOT so i must assume that there isn't an issue with the TPS as per your OP!

I would suggest you read the following contribution by this writer which is more descriptive than the YFSM (Yamaha Factory Service Manual):My methodology for checking your senario is the following based on your latest - 2nd response.

Enter into the Warrior diagnosis program (MMI) on the tach and verify the ENGINE (correction) & oil temps at ambient and also operating - hot temps.

These two devices are swapable so be careful not to stress the terminal ends and you'll need to reuse the sealing washers for the test.

According to the YFSM controls of the LCV reverts to the oil temp sensor after the engine starts.

If you don't trust the numbers in the MMI i would suggest exchanging the devices and see what happens.

Additionally, and if not stated clearly in the suggested LCV 101 reading, each and every time the engine is shut-down with the key the LCV closes completely. It actually tries to overclose if all is well.

I would expect but never have validated if an open terminal exists (Pin 21-22 & 43-44) to the ECU that it is reported at the MMI. I would also expect that the cold idle would not work properly either as the valve wouldn't work if one of the motor poles wasn't seeing negative polarity. The above is my opinion and understanding of this device and stepping motors.
good luck

Last edited by alanh; 10-28-2012 at 05:11 PM. Reason: typo-s/b engine and not air device
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Old 11-01-2012, 06:29 PM   #10 (permalink)
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Thanks for the LCV info. I went into the diagnostics and checked the engine and oil temp gauges. they both are giving out reasonable readings.

I played with the bike a little last night, and here' what i found:

Started the bike cold, and the LCV was open allowing it to idle high. once the bike reached temp the LCV started trying to close. I disconnected the the LCV intake hose from the air box to feel the air flow. The air decreases and then increases every second or so causing the idle to jump from 1100 to 1400. If i put my finger over the hose, the bike idles around 950 rpms. This tells me it is the LCV or something controlling the LCV.

Can anyone tell me what readings i should get at eh LCV wire connector when the bike is cold and warm. I want to see if the ECM is sending the correct signals the to LCV. I assume this would tell me if it is the LCV or another sensor or wiring issue.

Any other thoughts are appreciated.

thanks!
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