Introduction and idle speed question

Discussion in '6th Generation 2002-2013' started by roostercbrn, May 20, 2017.

  1. roostercbrn

    roostercbrn New Member

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    Hi All,

    Wanted to introduce myself and ask a question. A few weeks ago, I picked up an 03 VFR800 with a little over 12000 miles on it. It’s my first road bike. The bike is stock other than the handlebars and I believe the windscreen.

    I’ve done some general maintenance like changing the oil, air filter, coolant, and clutch fluid. While riding it, I noticed that the idle speed never changed as the engine warmed up, and that the engine temperature usually never got above 150F while cruising on the highway.

    I replaced the thermostat this weekend and the engine now properly warms up. Now that the engine gets up to temperature, I’ve noticed that it sometimes doesn’t want to start when it’s warm without me giving it some gas. The engine turns over fine, it just needs a blip of the throttle to get it going. After it starts, it temporarily idles around 1000 rpm and then picks up to around 1500 after riding a bit.

    I inspected/lubed the wax unit plunger and starter valve linkages this morning. It fired right up and was idling around 1500 rpm, which I’ve read is a little low for the cold idle speed. I manually moved the starter valve linkage to open the starter valves more and raise the idle to 2000 rpm and noted about a 1/16” gap between the nut on the wax unit plunger and the plate that the nut is supposed to be pulling on when the wax unit is cold. I was tempted to tighten the nut a few turns so that the wax unit opens the starter valves more to raise the cold idle, but the service manual says that you’re not supposed to adjust that nut so I left it alone. As the engine warmed up, I observed the wax unit plunger extend, but there was no drop in idle speed (which I believe is what’s supposed to occur).

    Anyway, I’m wondering if I should replace the wax unit or try and synchronize the starter valves. Any advice would be appreciated.

    Thanks!
     

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  2. Terry Smith

    Terry Smith Member

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    First thing I'd suggest is to pull the coolant hoses off the wax unit and make sure they are flowing freely, and flowing freely through the wax unit. The passages/hoses here are the smallest in the cooling system and have been known to get blocked. If anything this should give a high idle when warm, as the wax unit doesn't receive heating coolant.
     
  3. roostercbrn

    roostercbrn New Member

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    Thank you. I'll give that a try. I had assumed that coolant was flowing through the unit as the plunger extends when warm and retracts when cold, but maybe that was a bad assumption.
     
  4. roostercbrn

    roostercbrn New Member

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    Pulled the throttle body off. Coolant in both hoses attached to the wax unit and in the wax unit passage. I blew the coolant out of the wax unit and verified that there are no obstructions in the passage.

    Also for clarification, there are two apparent issues. My initial post was a little long and may have been unclear. The first is that the idle speed doesn't drop as the engine warms. The second is that it needs a little blip of the throttle to start when warm if I've let it sit for a few minutes. If I immediately try and restart the engine after shutting it down when warm, it usually doesn't need any throttle input. Not sure if the two are related or if they are being caused by separate problems.
     
  5. roostercbrn

    roostercbrn New Member

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    Put everything back together. Started right up when cold. Turned it off. Started right up again. Let it run a few minutes and shut it off. Came back in a about five minutes and needed to blip the throttle to get it to start. I put some Sea Foam in the tank and went for a 100 mile ride. It ran fine during the ride. Stopped to top off the tank when i got home and it started fine at the gas station. Let it sit in my garage for 15 minutes or so and then had to use some throttle to get it started again. Hmm.

    On a positive note, the gas mileage has improved now that I replaced the thermostat. I got about 44 MPG and that was with some liberal activation of the VTEC during parts of the ride.
     
  6. Terry Smith

    Terry Smith Member

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    When you restart the bike, do you allow the fuel pump to prime and stop before you hit the button? There should be a little residual fuel pressure when the engine shuts down, but it will bleed away slowly.

    Regarding the idle speed; it should (obviously) be high when cold, and drop to 1300-1400 when hot. The speed is always controlled by the starter valves, these are opened by the wax unit when cold then they rest on the idle screw when hot. Can you verify that the wax unit is not engaged with the SVs when hot? Does the speed when hot respond to the idle adjuster?
     
  7. roostercbrn

    roostercbrn New Member

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    After I switch the button to run, I always wait for the whine of the fuel pump to stop before I try and start the bike.

    As for the wax unit, I started it cold with the air box off the other day. If I wanted the bike to idle at close to 2000 rpm, I would have had to tighten the wax unit nut to get it to open the starter valves further. As the engine heated up, I watched the wax unit plunger and nut extend forward of the plate that the nut was resting on.

    As for the idle speed adjustment screw, yes, the engine speed responds to me turning it. I've adjusted the screw a couple of times after the bike is hot to try and set the idle speed to 1200-1300 rpm.

    One thing to note is that the engine seems to idle faster if I've pulled the air box off. Is that just because I've unhooked the MAP and intake air temperature sensors?
     
  8. Expvet

    Expvet New Member

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    I had a similar problem with my 2006. The idle was not rising much when cold started and would settle into about 1500 rpm and could not be adjusted any lower. I first lubricate the linkage where the idle adjustment meets the throttle bodies to get some motion with the adjuster knob. Then I lubricated the linkages at the wax idle unit. What really resolved the problem though was the discovery of a crack in one of the vacuum hoses. The hoses in general were a bit dry and brittle and I changed them all as a precaution (easy job). Since then my idle revs up when cold started and settles down to a nice 1300 rpm when warm. The crack was barely perceptible so changing the hoses at least eliminates that as a source of problem, especially on a 14 year old bike.
     
  9. roostercbrn

    roostercbrn New Member

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    Thanks for the suggestions, Expvet. I lubed the wax unit plunger, starter valve linkages, and idle adjustment screw while troubleshooting on Saturday. Everything seems to be moving freely. When the engine was cold, I had to manipulate the starter valve linkages by hand to get the idle up to 2000 rpm. When I did that, there was about 1/16" gap between the wax unit plunger nut and the plate that it is supposed to be applying pressure to in order to increase the idle when the engine is cold. Seems like the plunger isn't fully retracted when it's cold. I wonder if the unit can fail partially open.

    As for the vacuum hoses, that's a good suggestion. They do appear to be showing their age, but no obvious signs of a leak. Maybe I ought to buy a new wax unit and replace the vacuum hoses and see what happens. Did you buy the OEM hoses or did you just buy the correct type of hose and cut it to length? It looks like it's on the order of $50 to get all of the OEM hoses online. That's seems kind of expensive for some tubing, but what do I know.

    It started right up this morning and was idling around 1200 rpm. After a few minutes riding while going to work, it was idling around consistently around 1500 rpm. It's kind of odd that it initially wants to idle lower when I first start it up.
     
  10. Expvet

    Expvet New Member

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    Those were the same symptoms I had on mine, normal idle at cold start and higher idle when it warmed up. I changed the hoses with the the correct aftermarket type, the OEM hoses are nothing special. Just try to get whatever is the highest grade offered. The cracks don't really show themselves unless you squeeze and roll the hose with your fingers. Inexpensive and quick fix.
     
  11. roostercbrn

    roostercbrn New Member

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    Thank you for the suggestion.

    Today it was idling around 1300 when the engine was both cold and warm. Interesting how the idle speed seems to randomly change from day to day. I went ahead and bought some vacuum hose online, but I 'll have to wait until next weekend to replace it. If that doesn't work I guess I'll try the wax unit. I am also contemplating replacing the rubber boots on the throttle body.

    The fuel indicator started acting wonky today as well. Not that it's related to the warm hard start issue. With the tank full, it now displays 6 out of 8 bars. It was oscillating between 2 and three bars when I topped it off after work and the tank only took 1.5 gallons. I cleaned the electrical connection with contact cleaner but that didn't seem to change anything. I guess I'll probably put further troubleshooting of fuel indicator off until I solve the other problem since I can estimate the fuel quantity with the trip meter.
     
  12. roostercbrn

    roostercbrn New Member

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    The previous owner never did the wire harness recall. That wouldn't be related to the warm hard start, would it? I was going to have that done eventually, but maybe I should opt for sooner.
     
  13. roostercbrn

    roostercbrn New Member

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    Just an update. It's been hot this week (mid 90's) and when riding home from work after the bike has sat in the hot sun all day (there's no covered parking) I noticed that the idle speed wants to drop when the engine temperature starts to get to around 190 deg F. It doesn't seem to do this in the morning when the ambient temperature is in the 50's. After getting home I let it sit in my garage and watched the temperature creep up to 220. After letting it continue to idle for a few minutes the revs dropped low enough that the bike stalled. Started right up again with a blip of the throttle, but continued to idle low and would stall again if I let it sit there long enough.

    I replaced the vacuum tubing on the throttle body today in the hopes that it might remedy the starting/idling issues when hot. When replacing the vacuum line that goes to the fuel pressure regulator, a couple of drips of fuel came out of the line that attaches directly to the regulator. Maybe this is what's causing the hard start/stall at high temperature. A little bit of fuel leaking into the cylinder through the vacuum line when the engine gets hot. Took it out for a spin after putting it back together and it ran great, but I still have the hard start issue when warm after the bike has been shut off. Anyway, I guess I should replace the fuel pressure regulator next.

    I'm also going to sync the starter valves in the next week or two. Been reading up about how to do this. In the Honda Service Manual, it says to remove the MAP sensor from the airbox and temporarily connect it to the electrical connector along with the vacuum tube that's goes to the 5-way connector from the throttle body. Not sure why I would want to plug the vacuum line from the 5-way connector into the MAP sensor seeing as the other four lines that from the connector will be disconnected and hooked up to the manometer, which means that the vacuum line going to the MAP sensor is just going to be exposed to ambient pressure. Maybe the intent is to just have the MAP sensor electrically connected?

    Can anyone tell me if it's necessary to have the MAP sensor connected during the starter valve sync?

    Thanks.
     
  14. Expvet

    Expvet New Member

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    I did not have the MAP sensor plugged in when I did mine. Seemed to be the general consensus. Synch came out fine.
     
  15. sarge383

    sarge383 New Member

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    connect the map and warm up the bike after removing the air box. once warmed up then connect the manometer so you dont have to work on a hot engine for the whole procedure just hooking up the gauges. thats how i read it anyways. :Pop2:
     
  16. roostercbrn

    roostercbrn New Member

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    Thanks for the feedback guys. I'm kind of looking forward to doing the sync. It's been fun to learn about the bike by doing a lot of the work myself. I figure I'll wait to do the sync until after I've replaced the fuel pressure regulator, which I'm hoping will be here in time for me to work on it this weekend.
     
  17. roostercbrn

    roostercbrn New Member

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    Looks like the fuel pressure regulator was what was causing the hard start issue when hot. I removed the vacuum line from the regulator last Thursday after riding home from work and found that fuel was very slowly dripping out of the vacuum port. Installed a new fuel pressure regulator and the bike now starts fine when hot.
     
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