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Urbanengineer

VFR Slow to rev and bad low end response

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Hello Everyone, my VFR is slow to rev after a valve adjustment. I rechecked all clearances and that all VTEC lifter bypass spacers were removed, all vacuum lines routed correctly, and it is still slow to rev. Also notice, if I slowly rev up (1% per second) it hangs, bogs, and then surges up in revs to 5k. See that portion of the video from 0:13 on.

 

Notice how in the beginning I give it a ton of throttle and it doesn't respond? What gives? I'm running out of ideas and getting very frustrated. Thank you ahead of time for your replies.

 

 

 

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Could there be any chance your valve cam timing is slightly out? Could you have upset your starter valve synch? Vacuum line to your FPR connected O.K.? Absolutely sure no vacuum line is amiss? Very dirty air filter?

You obviously don't have any FI light warnings. 

Grasping at straws a bit here!

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6 hours ago, Grum said:

Could there be any chance your valve cam timing is slightly out?

 

And from your "Sanding Vtec Lifters'' thread:

Quote

 There was just a LOT of little issues getting it done (things I forgot to do, like keeping a tiny bit of pressure on the rear CC Guide so the cam gear doesn't skip a tooth when installing the gears.

 

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Gee thanks love. It’s right, I pulled it all apart and re-checked, the VFR has a finnicky valve adjustment and there are a lot of steps and catches. I made the mistake and shrugged, went back and fixed it. I’ve done a lot of other bike valve adjustments. Have you attempted it on a VFR? If you’ve done this rear head you would know exactly what I mean. 

 

I don’t believe I touched the starter valve sync, but to adjust those I was told the bike needs to be running well anyways so I probably couldn’t adjust them for now. Those are the adjustments on top of the throttle bodies connected to the wax unit, correct?

 

What is an FPR?

 

i tried it shortly air filter free, not an issue.  

 

No vacuum line issues as far as I know, no hissing or anything, I can’t really check too much. I could try spraying and looking for leaks that way I suppose?

 

I’m grasping at straws here or I wouldn’t bother you guys. 

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20 minutes ago, Urbanengineer said:

Gee thanks love. It’s right, I pulled it all apart and re-checked, the VFR has a finnicky valve adjustment and there are a lot of steps and catches. I made the mistake and shrugged, went back and fixed it. I’ve done a lot of other bike valve adjustments. Have you attempted it on a VFR? If you’ve done this rear head you would know exactly what I mean. 

 

I don’t believe I touched the starter valve sync, but to adjust those I was told the bike needs to be running well anyways so I probably couldn’t adjust them for now. Those are the adjustments on top of the throttle bodies connected to the wax unit, correct?

 

What is an FPR?

 

i tried it shortly air filter free, not an issue.  

 

No vacuum line issues as far as I know, no hissing or anything, I can’t really check too much. I could try spraying and looking for leaks that way I suppose?

 

I’m grasping at straws here or I wouldn’t bother you guys. 

"Gee thanks love" Sounds a bit sarcastic! Was just trying to help!

Thought you would know, FPR = Fuel Pressure Regulator!

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I take it there are no FI light codes flashing?

 

At low engine speeds the injection is controlled by the manifold pressure and the engine speed. If the MAP sensor hose was restricted or holed, I'm guessing you might see something like that. 

 

Don't call me "love" either. 

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18 minutes ago, Grum said:

"Gee thanks love" Sounds a bit sarcastic! Was just trying to help!

Thought you would know FPR = Fuel Pressure Regulator!

Never had to deal with one 🙂. I’ll check it out tonight. That wasn’t aimed at you it was aimed at the guy who didn’t read my post about me going back and rechecking all those potential timing issues that I mentioned I fixed while learning this adjustment. Thanks very much.

 

Actually I’ll ask, how does one test it? Resistance? Googling now. 

14 minutes ago, Terry said:

I take it there are no FI light codes flashing?

 

At low engine speeds the injection is controlled by the manifold pressure and the engine speed. If the MAP sensor hose was restricted or holed, I'm guessing you might see something like that. 

 

Don't call me "love" either. 

I didn’t reply to you yet bud 🙂. I called the quote guy love not you or the Grum! 

 

I appreciate the comment I will remove the line and blow it out tonight, check the MAP sensor for blockage, and check where it plugs in (I honestly don’t know, I think it went to a 5 way T?) and report back my findings tomorrow after work. I really appreciate the help. Can the MAP sensor be cleaned with carb cleaner or a sea foam bath?

 

I really want to get it running, it’s been a long winter of maintenance. 

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I'd expect the MAP sensor to either work or not, its not the sort of thing you'd clean. It's mounted on the back of the airbox and from the manual looks to go to a 5-way joint which then splits into 4 and goes to each intake throat. So if any of the hoses or the joint is split you might have a higher pressure reading that does not track the change in intake vacuum when the butterflies are goosed. 

 

This is from the 5G manual; my guess is the sluggish response is that the MAP pressure isn't changing much when you open the throttle a little, but when you wind it open more you get to the range where the injection volume is determined by the TPS instead. 

 

image.png.331623d83b65b8c6b8fa8a9320016291.png

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1 minute ago, Terry said:

I'd expect the MAP sensor to either work or not, its not the sort of thing you'd clean. It's mounted on the back of the airbox and from the manual looks to go to a 5-way joint which then splits into 4 and goes to each intake throat. So if any of the hoses or the joint is split you might have a higher pressure reading that does not track the change in intake vacuum when the butterflies are goosed. 

 

This is from the 5G manual; my guess is the sluggish response is that the MAP pressure isn't changing much when you open the throttle a little, but when you wind it open more you get to the range where the injection volume is determined by the TPS instead. 

 

image.png.331623d83b65b8c6b8fa8a9320016291.png

So you think the MAP sensor is doing fine, but the TPS is acting funny? How does one service that?

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54 minutes ago, Urbanengineer said:

So you think the MAP sensor is doing fine, but the TPS is acting funny? How does one service that?

 

No that's Not what Terry is saying. He has provided you information as to why there might be an issue with the MAP Sensor.

Do not attempt to spray the MAP Sensor with cleaning gunk. It is a sensitive Transducer converting Vaccum to electrical signals.

Also The FPR (Fuel Pressure Regulator) is not checked by Resistance, it is a Vaccum mechanical device. Why do you need to Google it? FPR, TPS and MAP sensor checks are all in the Service Manual. Would assume you have the full Service Manual for the 6gen.

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43 minutes ago, Grum said:

 

No that's Not what Terry is saying. He has provided you information as to why there might be an issue with the MAP Sensor.

Do not attempt to spray the MAP Sensor with cleaning gunk. It is a sensitive Transducer converting Vaccum to electrical signals.

Also The FPR (Fuel Pressure Regulator) is not checked by Resistance, it is a Vaccum mechanical device. Why do you need to Google it? FPR, TPS and MAP sensor checks are all in the Service Manual. Would assume you have the full Service Manual for the 6gen.

I don't have access to it most of the time on my cell phone, I am at home now reading it. I am trying to make sense of all of this.

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57 minutes ago, Urbanengineer said:

Okay, image attached of the "Fuel Pressure Regulator. Am I missing something? This looks tiny!

image.thumb.png.9f790e7f6aecf0034b071512a9ae7f28.png

 

Yes you have identified the FPR. Why are you suggesting it looks tiny from such a drawing? and who cares how big or small it is. Kind of, How long is a piece of string? comment.

"Am I missing something" - sorry I can't answer that for you!!

Glad you have found some video info on the FPR, hope that helps.

Are you sure you're an Engineer?

 

Good luck with your bike, hope it's sorted soon.

 

 

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I found a few things, including testing the one-way valve and such (vacuum). Tomorrow it going to be a ball of joy testing stuff.

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1 minute ago, Grum said:

 

Yes you have identified the FPR. Why are you suggesting it looks tiny from such a drawing and who cares how big or small it is. Kind of how long is a piece of string comment.

"Am I missing something" - sorry I can't answer that for you. 

Glad you have found some video info on the FPR, hope that helps

You sure you're an Engineer?

 

Good luck with your bike, hope it's sorted soon.

 

 

I can't have any fun, clearly. After seeing the video on it I would test it by pulling the vacuum line and going from there. I'm sure I could fuel pressure test it but that would require waiting for special tools for a one time use. 

 

I'm not a mechanical engineer, thankfully!

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Both Terry and myself have made mention of any Fi flashing codes.

If you haven't done this, connect a Jumper Wire to the Service Check Connector and see if there are any stored diagnostic fault codes. The procedure is easy to follow in the Service Manual.

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There were stored codes related to the injectors being unplugged. I cleared those and nothing new showed up. 

 

Turns out the MAP rubber hose has some splitting happening. I’ll replace it and see if that helps me.

 

Thank you for your help 🙂

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Hope that is it. 

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Well, after replacing that vacuum hose and putting all the stock parts back on everything seems to work well. 😁

 

Problem I notice now is that the flapper valve doesn't seem to be working. I removed it from the upper airbox and rode around with it connected to the vacuum line and it doesn't "retract" at any RPM. I suppose that means it needs to be replaced? I want factory type performance (flapper mod is always open flapper right?). If it doesnt work.. I assume it is likely vacuum line related. I followed the factory manual for how to run the hoses, triple checked 😢.

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The flapper is closed by intake vacuum and turned on/off by the solenoid, which gets it's instructions from the ECU. It should be closed in gear/clutch out below 5500 rpm/open above that, always open in neutral, or with the clutch pulled in, in gear; at least all of that is true for my 5G; for the 6G I know that things like the VTEC system only function when the engine is properly warmed up, so maybe the flapper is in the same logic?

 

You can check the physical function of the flapper with any source of vacuum, e.g.a brake bleeder, maybe even sucking with your mouth? If that works, then you may have a hose disconnected or the solenoid may not be connected. 

 

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39 minutes ago, Terry said:

The flapper is closed by intake vacuum and turned on/off by the solenoid, which gets it's instructions from the ECU. It should be closed in gear/clutch out below 5500 rpm/open above that, always open in neutral, or with the clutch pulled in, in gear; at least all of that is true for my 5G; for the 6G I know that things like the VTEC system only function when the engine is properly warmed up, so maybe the flapper is in the same logic?

 

You can check the physical function of the flapper with any source of vacuum, e.g.a brake bleeder, maybe even sucking with your mouth? If that works, then you may have a hose disconnected or the solenoid may not be connected. 

 

Huh! I wondered about that. Thought it was another symptom of my mechanic skills failing to check the VTEC unit or something... turns out the ECU tells it when it's okay to open up VTEC vales when building temp. Thanks for the knowledge.

 

I'll test the flapper tomorrow by putting the bike in gear. These bikes have a lot of stuff that could go wrong. Technology, folks! 

 

I appreciate your replies Terry.

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most riders with stupidly loud exhausts are guys in their 20's.  how old are you ?

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