LCV issue - Page 2 - Road Star Warrior Forum : Yamaha Star Warrior Forums

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Old 11-01-2012, 09:53 PM   #11 (permalink)
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Have you checked all hoses for cracks or leaks?

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Old 11-02-2012, 03:02 AM   #12 (permalink)
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Sorry this is so long. I decided to be explanatory because I'm very curious to learn what is happening to your bike. Partly I'm curious because there are some things the service manual doesn't say.

Take a minute first to look at the Service Manual. First, the top of Page 1-18; then Pages 1-28 and 1-29. These short pages will explain the LCV but every word is important and carries information. I'm guilty of having skimmed-over some parts of this and that made it hard on me to help others. So I kept asking annoying questions until a cool member (Churchkey) realized I was serious and he tapped me on the shoulder and pointed out what I was skimming over. So I read and re-read these pages and finally had the DOH! moment. I mention this only because when it happens to you, rest assured you are not the first and will not be the last!

The fact that you can hold your finger over the LCV's air input hose that connects to the stock airbox, and the result is normal warm idle, means that you don't have an intake leak elsewhere. There are no loose hoses or leaking gaskets. By default that means the extra air is entering via the LCV intake hose, which means the LCV is not fully closing. More than that, it means the LCV is probably stuck fully-open because a fully-open LCV will idle at about 1300rpm and when cold-idling the rpm will waver until the engine temperature increases.

So the next questions might be (a) is something making the LCV open-when-warm instead of close-when-warm; and (b) is the LCV actually stuck fully-open (remember that the engine rpm wavers and rises as motor temperature rises). The bottom line, if I may ask: Did you buy a new LCV from the dealer or a used one?

Before going any further, re-read this last paragraph on Page 1-29:
"In addition, the linear control valve fully closes when the main switch is turned off, but maintains its current position if the engine is stopped with the engine stop switch or if the engine stalls. When the engine is restarted, control starts at the maintained position." So if you turn off the motor with the key the LCV will fully close (it will go to its 'zero' or 'home' position). But if you turn off the motor with the kill switch then the LCV motor stays where it is and when the motor is re-started the LCV is still at the position it was at when the motor was stopped. I don't know if the ECU sends another command at start-up telling the LCV to fully close but it doesn't sound like it happens at start-up (or maybe the motor starting noises mask it). So maybe its possible the ECU tells the LCV to open to some extent after the motor has started and the ECU looks at the Oil Temperature Sensor?

It seems like you have already determined the LCV isn't doing what it should. We know that as soon as the motor starts running the ECU looks at the Oil Termerature Sensor for data used to send signals to the LCV to progressively close. The following isn't proven and I'm in the 'dunno' camp, but I have in the past questioned if its possible that the ECU might send a signal to the LCV that would make it re-open a little when the oil temperature sensor indicates the oil temperature is cooling. Like I said I'm still in the 'dunno' camp. If the ECU can re-open an already-closed LCV (like on a cold restart after using the kill-switch to shut-down the engine) AND if your LCV is working correctly, then a bad Oil Temperature sensor could explain what is happening to your warm-idle rpm.

There's no service manual indicator to support this, its supposition and seems like a long-shot so it seems a good idea to see Pages 6-16 and 6-28 to test using on-board-diagnostics. It seems most likely your replacement LCV is not exactly working correctly and there's no other ECU-LCV interface to explain the LCV's odd behavior.

Last edited by arizonawarrior; 11-02-2012 at 04:00 AM.
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Old 11-02-2012, 07:47 AM   #13 (permalink)
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Quote:
Originally Posted by rcoligan2 View Post
Have you checked all hoses for cracks or leaks?

The DarkMidKnightWarrior
I agree here, do this first. As the bike ages hoses do too. Always check the basics first.
Then get into details like the arizonawarrior posting.
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Old 11-02-2012, 02:25 PM   #14 (permalink)
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Help me out, I must be missing something! I was sorta thinking that if you plug the LCV's intake hose where it connects to the stock airbox and that alone causes the warm idle to drop to spec, well, it seems all the LCV hoses after that point (which means all LCV hoses there are) are not leaking because if they were then the idle would not drop to spec. It would not drop to spec because the leaking hose would be feeding intake air.

But if there is no leaking hose feeding air then it seems logical that warm idle will drop to spec when the LCV main intake hose is plugged ONLY if the LCV is drawing air when its warm and should be closed. Said another way, if nothing is leaking then the only thing left is the valve in the LCV body is not closing. Said another way, plugging the LCV system's air entry point at the airbox intake hose cuts-off the air only if there are no other leaks and if there are no other leaks and the intake hose is plugged then there is no air to pass thru the stuck-open valve.

Also, when air is flowing into the intake hose on a cold start, the more 'open' the valve is, the more air is passed thru. The more air that is passed thru, the higher the idle (the bike automatically matches fuel flow to air flow thanks to the air pressure sensors). I believe the cold-idle spec for the Warrior is 1300rpm maximum (thanks to my old PC3USB's software screen) although in the real world it will vary plus-minus something.

I only post this because there must be something I'm missing, is there another hose that could be leaking and still have warm idle drop to spec when the LCV intake hose is plugged?

Thanks guys.
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Old 11-02-2012, 02:58 PM   #15 (permalink)
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Quote:
Originally Posted by arizonawarrior View Post
Help me out, I must be missing something! I was sorta thinking that if you plug the LCV's intake hose where it connects to the stock airbox and that alone causes the warm idle to drop to spec, well, it seems all the LCV hoses after that point (which means all LCV hoses there are) are not leaking because if they were then the idle would not drop to spec. It would not drop to spec because the leaking hose would be feeding intake air.

But if there is no leaking hose feeding air then it seems logical that warm idle will drop to spec when the LCV main intake hose is plugged ONLY if the LCV is drawing air when its warm and should be closed. Said another way, if nothing is leaking then the only thing left is the valve in the LCV body is not closing. Said another way, plugging the LCV system's air entry point at the airbox intake hose cuts-off the air only if there are no other leaks and if there are no other leaks and the intake hose is plugged then there is no air to pass thru the stuck-open valve.

Also, when air is flowing into the intake hose on a cold start, the more 'open' the valve is, the more air is passed thru. The more air that is passed thru, the higher the idle (the bike automatically matches fuel flow to air flow thanks to the air pressure sensors). I believe the cold-idle spec for the Warrior is 1300rpm maximum (thanks to my old PC3USB's software screen) although in the real world it will vary plus-minus something.

I only post this because there must be something I'm missing, is there another hose that could be leaking and still have warm idle drop to spec when the LCV intake hose is plugged?

Thanks guys.
I was speaking generically, you know much more about this "open end" FI system on the Warrior.
I always check the basics(air,spark,fuel) BEFORE pointing the finger elsewhere, if you know what I mean. I am too dam old to chase my tail, cause I have done that way too much in my youth.
I am actually intrigued by this reverse choke system on this warrior. I will have to sit down with a beer and read your previous posts on the LCV.
The only problem I have had with idle is when mine was a lil high, I adjusted it down to about 800 to 850 and it helped a bunch. In fact I just took it down a lil in this cold weather. Mine starts quicker and lurches less with a lower idle,(no, not as low as a HD) not low enough to mash bearings, etc...
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Old 11-02-2012, 03:35 PM   #16 (permalink)
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Oh I see what you meant. I guess I didn't trhink about those basics because it didn't occur to me they might make the beast cold-start at the normally-high-idle and then increase idle rpm when warm. But I agree I should have suggested looking into the basics first and making sure the bike's baseline is properly set-up before messing with the idle adjustment. Thanks for reminding me!
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Old 11-05-2012, 04:29 PM   #17 (permalink)
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Ok. More trouble shooting. I reread the recommended pages in the service manual several times. My understanding is that if i turn the bike off with the key, the LCV should close completly. With this logic, I warmed the bike up, turned the bike off by the key and then disconnected the LCV wiring harness. I then turned the bike on to see if it would idle normally. the bike still was idling high (jumping between 1100 and 1400 rpms every few seconds). So the LCV is not closing. I put my finger over the LCV intake tube and it idled fine.

To answer a few of the above questions: the LCV i bought is a new OEM Yamaha part that i got at powersportsplus.com. I checked the onboard diagnostics and the engine and oil temp sensors seem to be reading normally. I could not get readings while the bike was runing so i could not see if the engine or oil temps were jumping around while the idle was jumping.

would anyone be willing to use a multi meter to test the 6 terminals on the LCV connector and tell me what the readings should be when cold and at temp? The would help me figure out if the correct signals are getting to the LCV.

Any other thoughts?

Thanks,
Chris

Last edited by hyper1685; 11-05-2012 at 04:57 PM.
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Old 11-05-2012, 05:18 PM   #18 (permalink)
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My guess is that you bought a used LCV, and if that is the case then it seems its bad, or debris-plugged so the valve cannot close. If you bought a new LCV then return it.

I don't think meter readings on the wires will help you. The manual explains how its voltage is understood by the ECU. [deleted mistakes in wire colors, should have looked them up first]

If you have used the On-Board-Diagnostics as shown in the service manual to test the LCV then between that test and your most recent result you seem to have a bad LCV assembly.

Last edited by arizonawarrior; 11-06-2012 at 12:36 AM.
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Old 11-05-2012, 05:36 PM   #19 (permalink)
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Thanks again. I edited my post to answer a few of you questions I missed. It's a new OEM LCV that I got from a place online. They have bad customer service and will not accept the return. They told me to take it the a certified Yamaha dealer to exchange which is next on the list. I though that it was unlikely that I would have 2 bad LCVs but I know it is possible. I will work on getting a replace. I do not want to have to buy a new one so hopefully I can find a dealer to exchange. I will let you know how it goes. Thanks again.
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Old 11-05-2012, 05:49 PM   #20 (permalink)
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Also, other will chime-in. I'm sorry to say that I have no other input because I don't see a path to make those things you posted happen unless there are error codes and/or unless LCV itself is bad. Hang in there.
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