Help please, power loss on a 00' model

Discussion in '5th Generation 1998-2001' started by Guest, Sep 23, 2003.

  1. Guest

    Guest Guest

    Hi all,

    my vfr 800 (2000, 14K km) has been in the shop for almost 4 months now and the mechanics still haven't found the cause of the problem. I've scanned the VFR mailing list archive and found a few owners with similar problems but unfortunately the posts didn't help much with the resolution.
    It all started with the bike running slower than usual at constant speed on the highway or when trying to overtake cars where the lack of power was somewhat obvious and where the engine didn't feel as crisp as usual.
    Eventually it ended up with the bike running like crap: typical example when starting from a traffic light, the bike would move forward very slowly (eg. refuse to take RPMs or would do at the pace of a 50cc scooter)even at full throttle, and sometimes would jump forward like a jet fighter on turbo for no reason.
    The mechanics have dismantled the bike and called me a few weeks ago saying they had found the cause of the problem: they had checked the fuel pressure gauge and the pressure wasn't in the recommended range. The part was swapped, I rode happily back home and half and hour later the bike was running like crap. Once again, same symptoms, very easy to notice when trying to accelerate on full throttle in a straight, the bike is relunctant to take rpm, and sometimes jumps forward just like if the power had come back.
    The mechanics have checked the fuel lines, coils, changed the fuel filter, changed the fuel pressure valve, and yet no sign of progress. They're now looking at the ECU but I'm not too optimistic.
    I'm lucky enough to have other bikes to ride but I'd really like to have the vfr back and the future doesn't look too bright, pls feel free to share similar experience.

    rgds,
    Phil
     
  2. Tourmeister

    Tourmeister New Member

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    Howdy Phil,

    I have a 98 that has recently been displaying these exact same symptoms. For me, it is intermittent. The bike will run just like you describe on one day, and then it will run perfectly fine the next. The bike has been flawless for the last 55K miles. I just had the 48K service done in May. As it has only recently started doing this, I have not really had a chance to get into the diagnostics very far. When/if I do, I will try to remember to come here and post what I find out. If you find a resolution, please do likewise ;) Thanks!
     
  3. Guest

    Guest Guest

    Hey Phil, if the mechanics are having trouble, they should work on Harleys!! I would recommend to start on the simple stuff first: plugs ( check the proper gap or replace ), air filter ( try a K&N ), octane booster, injector cleaner, etc. Depending on where you live, Can. or US, make sure you use good grade of fuel. The octane in the US is lower than in Can. I use Sunoco 94, or Shell 91. Other than that, it could be a problem with the fuel injectors, or the onboard computer.
    Hope this helps a little, let us know how things turn out,

    Ron
     
  4. Tourmeister

    Tourmeister New Member

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    Howdy,

    Unless you are running higher than stock compression or have messed with the ignition timing, there is no need to run an octane higher than 87. This is what the owners manual calls for. The ONLY thing a higher octane does is to prevent the fuel from igniting due to compression pressures before it is properly ignited by the spark. Older engines might need it because carbon deposits have built up to the point where they have actually raised the compression ratio of the cylinders beyond what it was originally. This is why many older engines knock and ping. Using a higher octane when it is not needed actually robs the engine of power and will reduce your gas mileage a bit. As far as engine detergents go, all of the major refineries now put the SAME detergents in all grades of their fuels. The idea of higher octane gas somehow being better for your engine has simply been a marketing ploy, pure and simple. The amazing thing is how well it has worked!? However, if you don't believe me, do a little research, ask any race mechanic, etc,... You'll find out the same thing. Or to get more personal, try the different grades in your bike for a while. The difference in both of my VFR 800's between the 87 and 93 is quite noticeable. I get about 2 mpg less and the bike does not pull nearly as hard through the rev range when I run 93.

    The suggestion to run through the basics is an excellent suggestion. It seems that mechanics today have horrible diagnostic skills. Without really knowing what the problem is, they just start replacing parts in the hope that the problem will go away. Four stroke engines are not that complex. They need very basic things to work. It may take some time, but the mechanics should be able to do a top down inspection to find the problem.

    The 98 that I mentioned in my previous post is now running fine. I believe it was moisture in some of the electrical connections that was interferring with the spark to one or more of the cylinders. With the equipment the dealership shops have, they should easily be able to verify if you are getting proper voltage to each spark plug, if the timing is correct, if the cylinders are reaching proper compression pressures, if the injectors are firing properly, etc,... But like I said before, proper diagnostics can take a little more time than the shop techs may want to spend. It is quicker initially to make an educated guess, replace a part, and hope for the best! Sad but true.

    I hope you get it figured out. Keep us posted.
     
  5. stephanon2whls

    stephanon2whls New Member

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    Synchronize the starter valves... It makes a big difference on smaller throttle inputs...
     
  6. bear

    bear New Member

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    One thing that can cause that is a plugged gas tank vent.

    As for the decreased mileage with higher octane fuel, do not get tricked by the decreased mileage due to methanol being added to the fuel. I have found that fuel with methanol added gets me about 10% poorer mileage. In Canada, Shell's highest octane fuel has methanol (as does Sunoco's), Esso does not.
     
  7. Tourmeister

    Tourmeister New Member

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    Note: regardless of the methanol, higher octanes do in fact lower the power and mileage for a given compression ratio. High octane fuels are used in racing applications because of the exceptionally high compression ratios on the cylinders. If they did not use the high octane fuel, they would experience pre-ignition of the fuel before the spark. This can destroy an engine. Old engines often need higher octane fuel because carbon deposits reduce the volume in the combustion area, effectively raising the compression ratio. This is why many old engines knock, it is the pre-ignition caused by not using the higher octane. VFR's are all designed to run on 87 octane per their users manual. Use of another octane is just wasted money on less power., unless of course your VFR is so old it has carbon deposits in the cylinders :p Most all of the major producers of gasoline now put the same detergents in all three octane levels offered, so that is not a reason to run premium any more either. Sadly, the "regular" and "premium" labels are just marketing tools to make people think they are putting better quality fuel in their precious vehicles. Running the premium doesn't hurt anything, it just costs more for less, hehe.

    Now having the other additives like methanol, that is just a load of political hogwash to appease the environmental fanatics :D Thank goodness we don't have that crap here in Texas!

    Oh yeah... did you ever get the problem taken care of?
     
  8. Georgiavfr800

    Georgiavfr800 New Member

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    Hey I got this one Nailed.. My bike had the same problem.. It was hard as heck to solve but it is solved.. ;D Hallalujah !!!! If you VFR begins to do this it is the Throttle Position Sensor.. One catch though Honda doesnt sell the TP sensor without the whole throttle body assembly >:( .. Thats a $1100 hit.. Ouch !! But, American Honda was nice enough to pick up the Tab.. What a swell bunch of folk.. !!!! I'd buy another Honda anyday if I have to deal with those folk again..

    Ghostrider
     
  9. Tourmeister

    Tourmeister New Member

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    Interesting. Was your bike under warranty still? I could see how a screwed up sensor might cause that problem.

    Adios,
     
  10. MP_Simmons

    MP_Simmons New Member

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    T'meister: I'm hip to the differences in octane , but please give me some rationale / documentation on how higher ratings may reduce power. My personal opinion is that primo is not overkill for an 11.6 : 1 mill if you want to make damn sure it NEVER knocks...
     
  11. Tourmeister

    Tourmeister New Member

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    Howdy MP,

    The only way using a higher octane fuel can "increase" power is if you run it in an engine with a higher compression ratio. This is why race engines use really high octane fuel. It allows them to run engines at some really serious compression ratios. However, for a an engine designed for a compression ratio that will work with 87 octane, there is no benefit to running a higher octance. Adding octane alone without also upping the compression ratio will not increase the power of the engine. Thinking that higher octane fuel is somehow "better" for your engine is misguided but very common. There was a time when using higher octane was better because it had the fancy detergents that would keep your engine clean, not because it made more power. However, all of the major brands of gasoline now have the same detergents in all levels of octane so that really doesn't matter any more.

    I'll poke around and see if i can find some online references for you. I seem to recall Kevin Cameron discussing it in his Sportbike Performance Handbook.

    Adios,
     
  12. Tourmeister

    Tourmeister New Member

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  13. bear

    bear New Member

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    All three articles are talking about only the fuel being changed. None address the increase in power when timing is advanced (within reason) in addition to premium fuel.
    With all else equal, premium will not help or add, but with other mods it may just.
     
  14. Tourmeister

    Tourmeister New Member

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    A nice succint summation. Thank you! ;)

    Now, back to the original thread!

    While out riding this last weekend on my 01 VFR, I started getting the symptoms described by the original poster. It felt like a cylinder was dropping! The bike sounded really odd, the throttle response was very sluggish, and occasionally it would revert to normal and take off like a rocket! Finally, it just started doing it constantly and would never revert to normal. Recall, somewhere in this thread someone mentioning that they had a TP sensor go bad and that once replaced, everything was good again. Well, here is a simple procedure to test for TP sensor problems,

    http://www.vfrdiscussion.com/scgi-bin/ikonboard.cgi?act=ST;f=8;t=280

    If the FI light blinks 8 times, you got a bad sensor. I am going to go home this evening and do this test on my bike. I'll let you know what I find.

    Also, anyone have any clue where the actual sensor is located on the bike? And what part number it is to get a new one?

    Adios,
     
  15. Scott_Lilliott

    Scott_Lilliott New Member

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    Hi TM,
    A quick check of the Service Manual shows that the connector to the TPS is attached to the TB of the #3 cyl (right rear). However the microfiche doesn't show the TPS as a separate obtainable part, as Ghostrider detailed earlier. Not a good thing IMO.
    Scott
     
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