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08 vfr keeps shutting off at lights.


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Just bought the bike. There is a broken fan switch on the bike that turns the fan on. It was working, but after going through the wiring and finding nothing we turned the switch on which turns the fan when ignition is in the on position. The fan turned off and on after reaching 190 for some reason but the bike didn’t die. So now I’m thinking it has to do with that. But I don’t know where to start. 

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Not too sure what you mean here. If a fan override switch has been fitted, then when that is switch to On it is overriding the thermoswitch and the fan will remain on until its switched Off or the Ignition is switched off. With the override switch to Off then the normal operation of the thermoswitch should be happening meaning the fan should swich on around 216degF, and Off around 207degF. Assuming the thermoswitch is not faulty.

 

The fan should have nothing to do with your engine dying at lights.

Are you saying your engine stalls whenever you come up to lights? Does the engine cut out at any other time?

Bit more info might help.

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49 minutes ago, BIGQ said:

It cuts out at lights or idle. Not when I’m moving. 

So when you start your bike and it warms up, what does your idle speed settle to, it should be 1200rpm engine warm. Or does it just stall/cut out on you?

 

And is this fan switch you're referring to is it an aftermarket override switch, or are you talking about the oem fitted fan thermoswitch?

 

Have you just purchased the bike privately or from a dealership?

Is this your first VFR800?

 

For info - If you don't have the Service Manual you can download it from this site.

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Just engine cut out, or 100% off?

 

I just went through an issue where dirty contacts in my ignition (switch under the key) and kill switch caused intermittent cut-outs.  If the bike is turning completely off, no headlights, etc., could be that.

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And when you say "cuts out" does that mean it dies abruptly or suddenly without warning or does it sputter or run poorly and then die?  

 

Also you did not  mention, but to be sure, you do not have a blinking FI light?

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vacuum leak

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My 2005 is also doing this.  While decelerating coming to a red light or stop sign, you pull in the clutch, the rpms go below normal idle speed and the engine stalls.  It always starts back up right away, but next redlight...same thing.  I spoke briefly about this to my local Honda shop and they said it could be the "Idle Air Control Valve."  Has anyone heard of this or know where it is on the bike?

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3 hours ago, 4li3nVFR said:

My 2005 is also doing this.  While decelerating coming to a red light or stop sign, you pull in the clutch, the rpms go below normal idle speed and the engine stalls.  It always starts back up right away, but next redlight...same thing.  I spoke briefly about this to my local Honda shop and they said it could be the "Idle Air Control Valve."  Has anyone heard of this or know where it is on the bike?

Absolutely should not be happening. Think you need to have the Starter Valves synch and idle speed adjusted. If you're not comfortable with doing the procedure then best to take your bike to a reputable Honda bike service center.

 

Did this start happening straight after your nicely cleaned and setup injectors were installed? That would have been the time to readjust the Starter Valves and idle speed when the good injectors were installed.

 

Starter Valve setup is mentioned in the Service Manual.

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5 hours ago, 4li3nVFR said:

My 2005 is also doing this.  While decelerating coming to a red light or stop sign, you pull in the clutch, the rpms go below normal idle speed and the engine stalls.  It always starts back up right away, but next redlight...same thing.  I spoke briefly about this to my local Honda shop and they said it could be the "Idle Air Control Valve."  Has anyone heard of this or know where it is on the bike?

 

What that shop told you is why so many of us (including me) never take our bikes anywhere for service - we learn to do it ourselves.  The 6th gen doesn't have an IAC valve!!  :blink:  That's why there is a manual idle adjustment screw extending down the right frame spar just to just above the clutch cover.  I might - might, give them a break and assume they're referencing the starter valves, but I seriously doubt it. The starter valves only control fast idle when the engine is cold, not base idle under normal operation.  Under no circumstances take your bike to that shop for service! 

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I should clarify that the bike is not doing this everyday. It reoccurs sporadically and I'm trying to figure out the circumstances under which it happens (cold engine vs. hot engine, etc.)  There seems to be no consistency so far. I don't think my idle speed needs adjusting as it normally is just fine at close to 1200 rpm after the engine warms up.  I also believe the starter valves are working properly as the bike cold cranks just fine, rpms a little higher while it is warming up and then properly comes back down once warm.  Do the starter valves affect the rpm after the engine is warmed?

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Just now, 4li3nVFR said:

Do the starter valves affect the rpm after the engine is warmed?

 

Not unless there is a problem - faulty wax unit, vacuum leak, etc. 

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The decreased idle and engine dying has never happened with the engine cold...it is after I've been riding a bit.  But it has happened on both warm days and cool days so it doesn't look like it is temperature related.  I bought this VFR as is with a Two Brother exhaust and a Power Commander III installed. I have never changed any of the settings for the Power Commander as I'm not sure how and don't have a manual for it.  Could the Power Commander settings be causing the problem?

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3 hours ago, 4li3nVFR said:

The decreased idle and engine dying has never happened with the engine cold...it is after I've been riding a bit.  But it has happened on both warm days and cool days so it doesn't look like it is temperature related.  I bought this VFR as is with a Two Brother exhaust and a Power Commander III installed. I have never changed any of the settings for the Power Commander as I'm not sure how and don't have a manual for it.  Could the Power Commander settings be causing the problem?

With your bike warmed up stationary (not riding), if you rev it to say 5000rpm then rapidly return the throttle to idle, does it nicely settle to 1200rpm or attempts to or does stall?

 

My thoughts regards your nice reconditioned injectors recently fitted, is that perhaps Starter Valves were attempted to be balanced whilst the injectors were in a bad shape, you now have good as new injectors. Fundamental to smooth idle and good slight throttle opening operation is starter valve synching then base idle can be properly set.

And as Cogswell rightly states check for any vacuum leak.

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9 minutes ago, 4li3nVFR said:

The decreased idle and engine dying has never happened with the engine cold...it is after I've been riding a bit.  But it has happened on both warm days and cool days so it doesn't look like it is temperature related.  I bought this VFR as is with a Two Brother exhaust and a Power Commander III installed. I have never changed any of the settings for the Power Commander as I'm not sure how and don't have a manual for it.  Could the Power Commander settings be causing the problem?

 

The starter valves which operate when the engine is cold, may be masking the symptoms until the engine warms as it ceases operating.  So it's not appearing to be related to ambient temperature, but it can be related to engine temperature until it warms and the wax unit closes off the starter valves and they no longer provide compensation for the problem.  If mine were doing this I would be first looking for a vacuum leak.  Check all the hoses around the airbox - that there are no orphan connections without a hose, the hoses are all in good condition, etc.  Same with the Pair system and vapor canister connections if either / both are still installed.   Also, no blinking FI light?  In the other active thread here about surging around 5,500 rpm, I mentioned going through the basics - check all those items are good.  Costs little to nothing to do.  Rule out as much as you can. 

 

You can go to Power Commander's website and download and install their software.  It's pretty easy to do.  Once installed, follow the instructions to plug in a USB cable and you can copy that loaded map off to your laptop.  If it's a pre-canned PC map, IIRC it will have the name associated with it.  The instructions will walk you through it.  Just get a baseline on what you have.   For the PC to work properly, it requires O2 eliminators plugged in to the harness, located under the alternator cover.  Just make sure everything is clean, tight and connected as it should be prior to rushing to conclusion about any cause. 

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3 minutes ago, Grum said:

With your bike warmed up stationary, if you rev it to say 5000rpm then let the throttle go, does it nicely settle to 1200rpm or attempts to or does stall?

 

My thoughts regards your nice reconditioned injectors recently fitted, is that perhaps Starter Valves were attempted to be balanced whilst the injectors were in a bad shape. Fundamental to smooth idle and slight throttle opening operation is starter valve synching then base idle can be properly set.

Grum, I believe that the bike returns to idle properly but I will try it tomorrow and post results. I am assuming that you mean with the bike in neutral and not going down the road?  Also I seriously doubt that they attempted a Starter Valve adjustment with the previously bad injectors... the bike wouldn't even crank and stay running until I had them professionally cleaned.  

Cogswell, I am not getting any FI errors that I know of but will make sure to notice next time it occurs.  Thanks for the school on what to check.  This weekend I'm gonna take a look under the hood? 😉 and look at vacuum hoses and whether or not the previous owner has done pair valve, snorkel, and flapper mods. 

Thanks everyone for the advice.  I'm sure eventually we'll find the culprit.

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3 hours ago, 4li3nVFR said:

Do the starter valves affect the rpm after the engine is warmed?

They can if not correctly set. Your starter valves provide idle bypass air to each cylinder when the throttle plates are closed. With a cold engine the fast idle wax unit uniformly acts on the starter valves to further open them(cold fast idle). Once warm the wax unit should no longer effect them as they slowly return to the warm idle position. The manual warm idle adjustment screw acts uniformly on all the starter valves to open or close them to either increase or decrease your warm engine idle speed.

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I've seen PC-III cause more problems than helped. As mentioned, download their tuning software and connect to PC. Inspect map and if there's any adjustments whatsoever, set it all to ZERO changes across the board.

 

Even so, that may not remove PC's effects completely as I've I seen lots of bad installs with poorly or incorrectly connected wires and shorts. I suggest removing PC and restoring back to 100% stock wiring to be sure.

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I can't complain about my PC III, it did what I wanted it to - smooth out low end throttle response,  but I had it dialed in tightly. I am now happier with my Rapid Bike. I get better mileage with it and response is at least as good or better. My 6th G rides as smoothly as my 4th gen did. RB is to Power Commander what the SH 847 is to a stock R/R.  Both PC and stock R/R are dated technologies.   PC has not kept up while RB has passed them by.  IMHO anyone that feels they need a tuning module to tame their bike's throttle behavior should go Rapid Bike. 

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On 4/30/2021 at 12:32 AM, Grum said:

Not too sure what you mean here. If a fan override switch has been fitted, then when that is switch to On it is overriding the thermoswitch and the fan will remain on until its switched Off or the Ignition is switched off. With the override switch to Off then the normal operation of the thermoswitch should be happening meaning the fan should swich on around 216degF, and Off around 207degF. Assuming the thermoswitch is not faulty.

 

The fan should have nothing to do with your engine dying at lights.

Are you saying your engine stalls whenever you come up to lights? Does the engine cut out at any other time?

Bit more info might help.


Mai I drove I to the dealer I got it from to have them look over it and I couldn’t get it to reproduce the symptoms. There is a switch that is on the black left plastic that broke the day I bought the bike. Replaced it with a new switch the night before and now it’s not doing it anymore. Bought another helmet and went home. If the problem comes back up I’ll give some more info.  

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