Fixed the problem. Fault, fuel pressure regulator.

Discussion in '6th Generation 2002-2013' started by New vfr boy, Jul 17, 2021.

  1. New vfr boy

    New vfr boy New Member

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    So I recently bought a 2002 Honda vfr800 after hearing how good these bikes were. But since I’ve had it, it’s not run right. The guy before me had a power commander and eliminated the o2 sensors. And it was running way lean. Too lean I’d say the standard operating temp was 210. I also suspected a misfire. Because the second day of ridding kind of took me by surprise it was having a stutter when holding the throttle at a constant rpm. So I took off the power commander and plugged the o2 sensors in. And then it ran super rich like smelling the unburnt gas bad. So much so I had 10mpg. I was running ethanol free then I put it down to 92 premium. I then replaced all the spark plugs and checked coils they all seemed fine. Then dude started valve adjustment and that seemed to help a little but now my issue it sputters and hesitates when holding steady when accelerating it sputters in almost any rpm range some times in first or second it gets to 7k rpms and it feels like it hit the rev limiter because it no longer wants to give power at all. Then when braking it will die sometimes and even just idling it will die. It also blew some smoke out the back when accelerating but only some times. Oil level hasn’t dropped and coolant has not dropped. So my last option before I completely give up and take it to a mechanic is to clean or replace the fuel injectors. And that’s the only thing I can think of doing but I’m unsure of myself because I have only recently been riding street bikes went from a 1985 gs450l to the vfr and I think I’m a little in over my head. Any help would be appreciated.


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  2. squirrelman

    squirrelman Member

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    you need to read the service manual. fuel pressure regulator is a common suspect.
     
  3. raYzerman

    raYzerman Insider

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    Yes, that...... but you mention valve adjustment..... are the cams in time or perhaps a tooth off?
     
  4. RllwJoe

    RllwJoe Member

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    How many miles on the clock?

    Start with the basics.
    - Take a look in the tank,..... any rust or other sediment?
    - check the charging system, wire harness, and grounding points,..... do The Drill, any sign of heat or poor connetions?
    (The Drill is found here : http://vfrworld.com/forums/showthre...mon-regulator-Stator-failures?highlight=drill - it is post #9)
    - How does the air filter look...... has a family of mice set up house in the air box, is the filter plugged?
    - Does it start well when cold? How long will it idle till it begins to stumble and what are the coolant temps when it does? If it starts well then stumbles when warmed up it could be an issue with the wax unit that acts like a choke.

    Your 02 VFR needs the same systems as any fuel injected car to run properly so don't be intimidated.
     
  5. New vfr boy

    New vfr boy New Member

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    So to answer some questions it has 27k miles on it. Cylinder 3 and 4 were off by a few clicks.

    The temps when running is 170 F and 185 F. It’s hard to start cold some days and other days it starts right up. When it doesn’t it needs some gas to get it going. It sputters no matter if it’s cold or warm.

    The fuel tank is clean, no rusting in the tank the drill looks fine. Air filter is clean and oiled.

    I have been around old cars and trucks and never really dealt with any injected motors. But from my knowledge of engines it doesn’t make a lot of sense because some days it will run fine and then later that day after cooling off it runs bad.

    So I thought it was injectors and I had no idea they had fuel pressure regulators. I’ll be getting down to the regulator and check and see if the vacuum line has fuel in it.

    She needs a little love from what I have seen as I look further into the bike the more problems I have found and fixed. But they are all minor things.


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  6. New vfr boy

    New vfr boy New Member

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    Also to clarify I did a synchronizing of the starter valves


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  7. RllwJoe

    RllwJoe Member

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    So the "valve ajustment" mentioned in your first post was a syncronizing of the starter valves.

    You say that #3 &4 were "off by a few clicks". According to the Honda service manuel, if I remember correctly, all four of them are set at different levels. They are not soposed to be the same. You didn't adjust them to be identical did you? Also, I don't believe that they have much effect on the the fueling beyond partial throttle.

    You were thinking that it was running "way Lean" based on the coolant temp being atound 210. That sounds pretty normal if in stop and go traffic where air flow is minimized through the radiator.

    The fuel regulator is a possibility as raYzerman suggested.

    You didn't mention seeing a yellow FI light on the dash while running. If you do you can check the built-in diagnostic code for an indication of what may be off.
     
  8. Terry Smith

    Terry Smith Member

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    Starter valves on the 6th gen are all set to an even vacuum. Only the 5th gen has the offsets.

    The fuel pressure regulator sounds like a possible cause as this has a vacuum-operated diaphragm; if that ruptures, raw fuel gets sucked into the intakes through the vacuum hose, and the normal fuel pressure to the injectors will be running high. You can simply check the rubber vacuum hose off the regulator and see whether it has any raw fuel in it. If the vacuum hose is missing/loose/split, that would also give over-rich running.
     
  9. New vfr boy

    New vfr boy New Member

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    Yeah I say running lean because that 210 was at a 78d degree temp outside and at 40 mph. I’d say that’s hot and it smelled like Copland that’s burning off from evaporation. Or kinda like how my old truck smells because it’s running to hot. That was my looks at it. And like terry said they were all supposed to sync off of the one cylinder that can’t be adjusted. I’ll get a new fuel pressure regulator tomorrow and replace it. I have not had the opportunity to check it since I posted but it sounded the most likely. Thank you all for helping this poor guy out haha. I do well with old trucks and cars but anything that has to deal with computers in cars I’m at a loss. Also my f1 has not given off a code not sure if it’s just not working or not but the light comes on when I first turn the key and shuts off after it primes the system


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  10. RllwJoe

    RllwJoe Member

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    I have only adjusted mine, a fifth gen. Thanks for clarifying the difference.
     
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