Possible fueling problems

Hey folks,

So I think I have a fueling problem with my 6th gen. Naturally the symptoms started just after I installed the new performance headers and was starting to enjoy riding with them. I believe this is coincidental though, based on the symptoms. Which are:
- rough idling
- very poor low rpm performance (sputtering, missing, no backfire though), IOW, hard to get rolling w/o feeding in a lot of throttle to bring up the rpms
- relativly smooth running once moving, but seat of the pants performance feels sluggish. And when the throttle is let off, I can feel the engine get rough
I realize the description of symptoms is not very clear, but maybe someone has run into something similar and has suggestions. The issue did not come up on the first few runs after I installed the headers, but started a bit later.

No codes are being thrown ... yet. I have a RB unit with the std map supplied when purchased. I also have the RB module that can be put in place to restore the OEM mapping. I put the RB OEM module in place this morning, and that did not help. I have given a little thought to fuel quality, however, I normally run non-ethanol premium (RB map recommends premium) from a known source, so I don't think that's it. The bike does not sit outside either.

I am looking at using the 'shotgun' approach to get back to normal 'quickly'. I'm thinking of replacing the following items:
- fuel pressure regulator
- fuel filter
- wax unit (not to address the problem, but b/c I'll be in there anyway)
All of these items are presently original, and have ~40000 miles on them. My gut is telling me that the injectors are not the problem, I could be wrong though. I guess maybe coils could be the culprit? My voltage monitor does not indicate a problem in that area, but ...

The fuel pump is not on the list yet as it seems to be working. If I were to pick up a fuel pump, I'm looking at these folks:
www.highflowfuel.com
They list an OEM compatible pump for the VFR800 for $69.98. Does anyone have any experience with this distributor?

Anyway, if someone out there has suggestions on where to look, things to try, etc., I would appreciate same.

Thx for reading,
ACE
 

Better exhaust system means more flow, which means (maybe) that installation of the New Header has given you a lean-idle condition.  Does your RB module allow you to rich-up the idle fuel supply?

52 minutes ago, GreginDenver

Better exhaust system means more flow, which means (maybe) that installation of the New Header has given you a lean-idle condition.  Does your RB module allow you to rich-up the idle fuel supply?

I'm sure it does thx, haven't looked at the SW in a while.  I should probably have spelled out RB, RapidBike, some here are familiar with this unit. Funny thing is I swear I smell more fuel idling in the driveway, as in richer, which makes no sense then.

1 hour ago, carlgustav

I'm sure it does thx, haven't looked at the SW in a while.  I should probably have spelled out RB, RapidBike, some here are familiar with this unit. Funny thing is I swear I smell more fuel idling in the driveway, as in richer, which makes no sense then.

Well, if the bike has gone all stinky-rich at idle (which you didn't mention in your original post) then you should ignore what I said and instead suspect that perhaps the RB module (or the Honda PGM-FI ECU) is confused by the mixture-ratio that's being induced by the New Header and is overcompensating.  Sometimes an O2 sensor that's experiencing an "off-scale" air/fuel ratio will default to a really rich or really lean output reading.

@carlgustav  my bike went a little richer at idle with the new headers, too.  I was checking with my rapidbike wideband sensors.

I haven't talked about any of this because I haven't really worked on it, but I started looking at fueling last week after putting the headers on. This was because of a different problem started to become accentuated. By that, I mean that I think it has been coming on for a while, but now I really notice it and it is getting much worse.  

I'm actually getting slightly inconsistent power delivery in the low-mid range cruise area, like 5K and 5% throttle, and sometimes, not always, it will go a little rough in that area and feel like I've lost some power.  At higher revs it seems fine, but at lower it is getting to be a noticeable issue and seems to be getting worse.

I've got the RB  and a wideband sensor, so I know for certain it's rich there. I've looked at my fueling in the driveway and it'll show like 10.6 as I hold it at some rev -- 4000K maybe -- then it'll go up to 11.5, 12, 12.5, then maybe back to 9.5. If I enable correction in that range the rapidbike will spin it up, maybe 10% enleanment trim, but then it'll start to lean off almost at random and RB will have to correct, but then again it'll get back to rich and so on. This will happen with stock sensors bypassed, so Honda isn't changing the map. It really feels like fuel flow is inconsistent, and I have a new FPR and did my injectors last year, so I don't think those are culprits.

Having read the fuel filter thread linked below I have decided to change my fuel filter. I had thought it was new when I bought the bike, but I confirmed with PO he didn't do it, so that's an 18 year old item right there. New one is on the way, so I'll change it out over the weekend and see what happens.  I know it seems counter intuitive that restricted fuel flow makes it go rich, but it is possible it is correcting the lean condition then when the flow gets good again I'm going rich. Haven't explored this, though, just bought the fuel filter and will look into it all when I've changed that mess out.

I'll report back here what my results are.

Now, I have a couple of questions. 

1. When you downloaded "the map" don't you have sensors hooked up to your RB ?   Mine used the stock sensors to trim before I got the wideband and My Tuning Bike installed, so the only maps I ever got from RB were ignition maps. I built the rest off of the stock narrow band sensors.

2. Very low RPM -- is this below the threshold where your rapidbike starts correcting? So at that point it is using stock fueling?

I am assuming since you restored stock mapping that your issue is fundamental, not the RB module.

I appreciate the feedback.

@GiD; sorry about not mentioning fuel smell, it's hard to remember all the little anecdotal things I notice after I'm off the bike for a bit, and then post. Another anecdotal bit, my fuel guage displayed level appears to be dropping much more rapidly than 'normal'. Over 10 yrs of riding her, I've gotten a 'feel' for how the guage 'acts' (I think we all get a 'feel' for our bikes behavior, don't we), and it ain't right at the moment. Very non-scientific observation and my mind could be playing tricks as I wasn't expecting any issues in the first place :biggrin: .

@MM; I installed my RB years ago, just the harness and the unit with the map developed for the VFR at the time, using the stock O2 sensors (2 on my 6th gen). I downloaded the map and had a look back then, but did nothing to it. She has run like this until now, without a hitch. Very low RPM for me means, idling in the driveway, and pulling away in 1st gear, although pulling away requires running up the throttle to keep from stalling. Once up into 2nd, she ran better, but that seems to be getting worse now also. Without going back to the original map I pulled down, I'm not sure what the correcting threshold is. If you're getting the impression that I'm a 'set it and forget it' kind of person, you would be right :laugh: . I will have to pull out the map, the SW, etc., and have a look. And yes, even with the RB 'return to stock' module, the symptoms did not go away. I could remove the RB stuff completely, restoring all stock connections, and see what happens. It will be interesting to read the results of your fuel filter replacement. Your statement about having a new FPR, and clean injectors, and experiencing the symptoms you note, makes me think I'll just replace the fuel filter.

I guess I'll have to do some work ... nuts. This is my one bike I rarely have to 'fix'.

ACE

2 hours ago, carlgustav

makes me think I'll just replace the fuel filter. 

Yeah, that's where I'm starting.  Mine came in the mail yesterday.

Let me know how it goes for you. I'll do the same.

3 hours ago, MooseMoose

Yeah, that's where I'm starting.  Mine came in the mail yesterday.

Let me know how it goes for you. I'll do the same.

Will do.  Although I just ordered mine and it won't be here till next week (2 - 5 days).  Gives me time to look at various areas while I wait ...

Interesting little sidelight here.

I drained the tank and put in the new fuel filter. Haven't had a chance to ride it. Ran out of light putting it back together, so I guess I'll find out how it goes after the storm tomorrow passes.

However, while inspecting everything I did find something interesting. The vacuum line to my fuel pressure regulator was a bit bent. Not enough to cut it off completely, but possibly enough to make for inconsistent vacuum.  I guess when I put the airbox on last time I got it pressed beneath another vacuum line and it was pulled downward.  I routed it above that other line now  so it doesn't have a sharp bend coming off the FPR, so... yeah. That could easily have been the reason for inconsistent fueling.

Intuitively, it seems this could be the culprit. The way the FPR works is to keep fuel pressure at 36psi above manifold pressure. That's what the second pair of vacuum ports on the throttlebody is for, to provide the manifold negative pressure.  As the vacuum pulls on that FPR it counteracts the spring holding the diaphragm closed so if the difference is MORE than 36psi the diaphragm opens and lets the fuel flow into the return line.  Ergo... if I'm not pulling my regulator open soon enough with vacuum, I'm going to run too high a pressure in the fuel rails, which would explain my rich condition at lower RPM. Higher RPM with the throttle open there's enough vacuum to swamp the effects of a partial restriction on that vacuum source so corrections  don't need to be so great, but at 5% throttle heck no. There's very little vacuum here at idle.  So, that's my working theory. I state it here before I've tested it, so I may be full of crap. We'll see.

Next time I pull the throttlebody, I think I'll put a longer line there and route it slightly farther around so it won't ever kink even if I do get it squished between the hoses for the reservoir and one way valve/solenoid. I do want to replace the breathers for my starter valves, so I have to yank it the TB off some time. Another item on the project list.

Also, fair warning. Getting the filter/pump  plate out  and back in kind of sucks. The rubber boot around the prefilter really has to be crammed in there. Come on Honda, could you REALLY not find another half inch there to make removing and replacing a little more elegant?

9 hours ago, MooseMoose

Intuitively, it seems this could be the culprit. The way the FPR works is to keep fuel pressure at 36psi above manifold pressure. That's what the second pair of vacuum ports on the throttlebody is for, to provide the manifold negative pressure.  As the vacuum pulls on that FPR it counteracts the spring holding the diaphragm closed so if the difference is MORE than 36psi the diaphragm opens and lets the fuel flow into the return line.  Ergo... if I'm not pulling my regulator open soon enough with vacuum, I'm going to run too high a pressure in the fuel rails, which would explain my rich condition at lower RPM. Higher RPM with the throttle open there's enough vacuum to swamp the effects of a partial restriction on that vacuum source so corrections  don't need to be so great, but at 5% throttle heck no. There's very little vacuum here at idle.  So, that's my working theory. I state it here before I've tested it, so I may be full of crap. We'll see.

Yes, you've made a connection most people just don't get: That for a given fuel injector "pulse width" (commanded by the ECU) any increase in fuel pressure (even just a slight increase, delivered by a slowly mechanically failing FPR or an FPR operating in a vacuum-starved condition) will deliver a richer mixture to the cylinders.

My '99 5th Gen has a late-1998 production date on the VIN sticker, which means the bike is now 21 years old.  Who knows how long the diaphragm inside the FPR was designed to last?  I don't know.  Does the spring inside the FPR stay in perfect factory calibration forever, or does it slowly lose that original calibration?  I don't know the answer to that either.  What I do know is that my '99 5th Gen often gives off a stinky-rich smell when I'm sitting at stoplights and stop signs.  Some of the bike's components are considered "consumable items" and are meant to be treated as such.  Things like fluids (hydraulic and coolant and engine oil) are the most obvious and often replaced, but other things are consumable on a much longer timeline.  The FPR is one of those.

As mentioned, I really don't know how many years the VFR800 FPR is intended to last, but I've decided that now, at 21 years, is where I'm making the call.

[image: IMG_20190519_092329_zpss096x0sf.jpg]

I'm combining this FPR replacement decision with: 1. cleaning the carbon off of the backsides of the intake valves, 2. having the fuel injectors professionally cleaned and evaluated.  While at the same time installing the New Header system and replacing the water pump due to a failing/slow-leaking shaft seal.

I don't disagree with the FPR and age. I replaced mine early on when I did my injectors on similar grounds. I had no clue that it was bad and, frankly, it was probably fine. I've kept it as a spare. But I was there so I did it. Same with my thermostat, though the old one worked fine and tests perfect. Mostly I didn't want to have to pull the throttlebody again, which is funny as I've had it off half a dozen times since. But having seen the condition of o-rings on the knuckles inside the V, I don't trust any rubber 20 years old that I can't see for myself.

As a side note, the rubber stuff in the fuel tank is all in great shape. I don't know if this matters for a FPR diaphragm, but heat on an O ring sure makes things worse.

All that said, don't count on this being the culprit until the weather dries up and I can put the bike back together.  I'm literally a driveway mechanic, and it rained this morning, so I haven't had a chance to finish up.

Anyway,  I have been very focused on this vacuum system so I may be missing something else. When all you have is a hammer every problem looks like a nail. You might remember that you guessed I'd start throwing MAP codes, which turned out to be true, and I replumbed the vacuum lines, which stopped the codes. So, yeah, this leads me to a few ideas about my poor mileage.

1. I was getting less than 30 after the MAP codes started going off.

2. I was still getting poor mileage before the MAP problem was bad enough to throw codes

3. Replumbing the vacuum fixed the MAP codes, no new sensor needed

So, to start with, if the vacuum leaked enough to cause the MAP codes, maybe it leaked enough my FPR was running too high a pressure across the board. I can't imagine that the FPR hoses were any better off than the ones running the sensor.

After fixing the MAP I didn't really get good mileage. Better, but oddly better when hauling ass and not when cruising. But I only ran one tank before pulling the airbox to inspect things, so I could have partially kinked that hose even then.

So, mileage improved, but only a little, and the rapidbike corrects less at higher RPM, but now I get a huge correction at 5% throttle. I think I fixed my default (rich) map at idle and still created a different too-rich condition at 5% throttle and less. the intermittent nature of my issue definitely lends credence to the partial blockage theory.  And I don't know what else to check.  heh.

The new headers seemed to accentuate the problem a bit, but that has to be unrelated beyond just the minor differences. They are super high quality, don't leak, and I'm certain I'm getting valid enough lambda sensor readings. So that's totally out of the equation here. I had honestly wondered if my old headers were giving bad readings from leaks (they occasionally got a little leaky after a high temp run -- the Delk's have a LOT of slip joints) but think that was a red herring now. These pipes seal and work well.

I could philosophize a lot, but either way I screwed up kinking that hose and fixing it (just like fixing the vacuum leak in general) will be a net positive. Gonna grab lunch and hope the sun shines so I can put the tank back on this evening.

I think you ate going about this all wrong. If your bike worked fine before the exhaust header change, then there is your issue.

The new header will flow very different to the old & the fuelling will need to be adjusted. To do this properly, you should cap the PAIR system, ensure the new exhaust is sealed at all joints & remove the stock O2 sensors if you have the MTB for RBR. 

I swapped TB's & injectors on my & it was rough as a dog off the bat. 45 miles of mixed riding with the MTB set to +/- 15% fixed it.

YMMV 

Quote

I think you ate going about this all wrong. If your bike worked fine before the exhaust header change, then there is your issue.

I 'removed' the RBR unit (I do not have the MTB) Sat, and rode around long enough to note that the same symptoms are still present. So at this point, based on your feedback, I probably should swap the headers back and see what happens. Crap, this goes along with the idea that 'when a new problem occurs after doing something, go back to the last thing you did'  :laugh: .

I have the stock ECM (ECU?) in play, tank loose and flipped around for access, and airbox removed. She fires right up but I haven't run her more than a couple of seconds. Sure looks wet down around the valves, but I'm assuming start up fueling is doing this (now throws a code too of course, IAT disconnected, etc). I have a new FPR and fuel filter on hand. Would it be reasonable to just go ahead and replace these while I'm there? Seems like the answer is yes, but this may add another variable to problem?

I've seen suggestions to pull the plugs and examine when you have running issues (makes sense). Maybe it's just old school thinking, but don't you have to do this after shutting down immediately following a run with load? Doing so is not practical for me.

ACE

Could you do me a favor? Before you pull the headers, at least check them for leaks.  That's the one thing that could be off with a fresh set of pipes.

Just plug the tailpipe and see if the bike shuts off. That's how I could tell when my Delk headers were leaking, it'd barely run, but it would still run because it could expel pressure out one of the joints.  If you're all sealed up it'll die.

Also, I took a short ride yesterday evening. It is a lot smoother. Alas, I don't know if that was fuel filter or FPR because I discovered the kinked vacuum AFTER I had installed the fuel filter. 

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Could you do me a favor? Before you pull the headers, at least check them for leaks.  That's the one thing that could be off with a fresh set of pipes.

@MM, sure, sounds easy enough. In ref to your vacuum line discovery, mine all appear to be good so nothing there to do.

ACE

So the bike will NOT run properly with the new headers if you don't adjust the fuelling. So you need either a PCV or RBR. It definitely will not work properly with the airbox removed, as there are 2 sensors attached that are needed to supply the Fi with data. The stock O2 sensors will take way too long to adjust to correct fuelling. So if you want to keep them get the RBR back on & get it to a dyno to fix the fuelling. 

Yeah, I just rode at lunch after clearing my maps, let it correct again after plenty of cruising at 5K rpm.  It corrects enough to run lean now. Really smooth, good throttle, and consistent.  If you have the filter and FPR on hand, replace them.  It may not be your problem, but if you already have the airbox off and the fuel tank off... there will never be a more opportune time.

I may have another issue to chase, but I won't bring that up here. I've already muddied these waters.  But I want to emphasize that one or the other (or both) of my FPR/fuel filter changes have brought a marked improvement in the hesitation and inconsistent running in the midrange for me. 

@Mohawk your point is well taken, but  this bugs me:

Quote

rough idling
- very poor low rpm performance (sputtering, missing, no backfire though), IOW, hard to get rolling w/o feeding in a lot of throttle to bring up the rpms

The rapid bike doesn't touch fueling at idle. Or below whatever your cutoff is, or at closed throttle.  Rough idling is NOT a symptom you'd expect just from these pipes. They're not that different, and at idle you're running closed butterflies and feeding it via the starter valves. It should already just run slightly rich and a change in diameter of the primaries is NOT going to change AFR requirements at idle enough to muck things up this much by itself.

That said, I'm flummoxed.  That's why I suggest changing FPR and filter *now*, since they are normal maintenance items anyway. Check the pipes are properly sealed. If all that doesn't improve, yeah. Go back to the old headers and see if that improves it.

@Mohawk; there is a dyno guy in my area but I have no experience using him. He tunes built sports car motors, and HDs. I spoke to him and he said he could look at the RBR SW if I bring my laptop out, and see what he could do. That was just before my bike crapped out, so I have to get her running well enough with the new headers to get to his shop. And I do understand that she's not meant to run right with no airbox, sensor connections, etc.

@MM; I ran the motor at idle just long enough to put a piece cardboard over the header outlet, tight, and she did not stall or die. However, holding a small piece of kleenex with a roach clip near each head pipe, it didn't flutter. If there's a leak, it ain't much. I'll go ahead and replace the items I have, since I'm there as you say. I have the stock air filter, but shining a light thru it indicates it's rather clean.

I have a new laptop, so I have to find my copy of the RBR SW, and my original map, to put on it. I may have to consider a MTB module, but I suspect they're expensive ...

ACE

At this point I'm wondering about which type of gaskets you used when you installed the New Header.  If you used the 42mm copper gaskets from Delkevic they might be part (or all) of the problem.  Did you see the thread (with pictures) that I posted when I was trying them?

2 hours ago, carlgustav

@MM; I ran the motor at idle just long enough to put a piece cardboard over the header outlet, tight, and she did not stall or die. However, holding a small piece of kleenex with a roach clip near each head pipe, it didn't flutter. If there's a leak, it ain't much. I'll go ahead and replace the items I have, since I'm there as you say. I have the stock air filter, but shining a light thru it indicates it's rather clean.

If it doesn't shut off, you have a leak. It's possible it isn't enough to cause problems and not enough flutter something up there. It's also possible you're leaking at the slip on or connector. But, this could be part of the issue. It's a problem long term either way as it could lead to faulty readings for your rapidbike.
 

As an aside, Greg, I know you seem to have an issue with 42mm gaskets, but you're the ONLY one.  And you never even finished your install to actually test whether properly installed 42mm would have sealed on your bike.

So far several other people have installed these with those 42mm gaskets. I specifically know SF has done it half a dozen times on 6th gens, 5th gens, and I think an 8th gen, all using this 42mm Delk gasket. Duc has done it a couple of times including on his 5th gen. I've done it on a 5th gen and, though one was a little tight, it went into the port as I tightened the nuts and I got a good seal on all four the first time. Now, it's entirely possible that carl doesn't have a good seal for some reason or other, but so far 42mm Delk gaskets have worked for everyone else.

Anyway, here's what you should expect (Again, this is 42mm delk gaskets). It shuts off post haste.

Ok, mine sure did not behave like the bike in the vid, so there's that. I'll replace my maintenance items, then drop the new headers to look over the gaskets. I may have boogered one or more up on install.

I never tried that test with the old headers, might be interesting (to me) to see what happens. A bit of work but she's stripped down and on the lift already. It's riding, not wrenching, season damnit  :biggrin: .

Thx,

ACE

12 hours ago, MooseMoose

If it doesn't shut off, you have a leak. It's possible it isn't enough to cause problems and not enough flutter something up there. It's also possible you're leaking at the slip on or connector. But, this could be part of the issue. It's a problem long term either way as it could lead to faulty readings for your rapidbike.
 

As an aside, Greg, I know you seem to have an issue with 42mm gaskets, but you're the ONLY one.  And you never even finished your install to actually test whether properly installed 42mm would have sealed on your bike.

So far several other people have installed these with those 42mm gaskets. I specifically know SF has done it half a dozen times on 6th gens, 5th gens, and I think an 8th gen, all using this 42mm Delk gasket. Duc has done it a couple of times including on his 5th gen. I've done it on a 5th gen and, though one was a little tight, it went into the port as I tightened the nuts and I got a good seal on all four the first time. Now, it's entirely possible that carl doesn't have a good seal for some reason or other, but so far 42mm Delk gaskets have worked for everyone else.

I'm an Airline Transport Pilot, the highest level of certificate.  For 20 years now I've made my living flying your family around.  Plus 20 years as a military pilot.  I take maintenance seriously.

When I discovered that the 42mm gaskets were slightly oversized for the cylinder head exhaust port seats and and saw that under the stress of the install-crush they were undergoing serious deformation: doing things like bulging into "out-of-round" shape at the sections of the front cylinder head exhaust ports where there's no retaining sidewall, and actually being "unrolled" against the retaining sidewall by the force of installation in the rear cylinder head ports, I pulled the plug on using them.

I didn't say anything about whether or not you might be able to get lucky with these gaskets and achieve a good seal at all four cylinders.  But using a part that doesn't quite fit and depending on some luck to bring it all together isn't my style.

So far I've only seen how the 42mm gaskets behaved during my test installation on my '99 5th Gen.  Show me some "after" condition pictures of the 42mm gaskets performing flawlessly on other bikes and I'll STFU.

Come on Greg, nobody is telling you the shut the fuck up. You should know by now I appreciate who you are.

I just find it strange you're caught up on this.   And, as for "flawless" performance, I've shown you a video of my leak free bike. You also have SF and Duc;'s word that their bikes work properly. They took pics of the gaskets on the way in, but didn't post in between pics when they were pulling one header and attaching another I guess. Ping SF and ask him if he has photos of the crushed gaskets if you care, he tested a bunch of different gaskets,  but this is not "getting lucky" this is good experiences advised by people who do exhaust for a living and repeated  a dozen times by those of us lesser mortals who have only done headers once or never before this exercise.

There's a difference between making a decision between valid options and "mine works and you just got lucky."  I think you did the former -- chose the smaller gasket because you were willing to live with the smaller id of the crushed gasket. But it's kind of hard to say that the larger gasket doesn't work when, clearly, they do.

Also, I saw your thread. You installed one or two of your test gaskets backwards. If you'd put them seam in they would have performed differently and I would guess better. And, frankly, I had a slightly tight fit on one cylinder in the back, but mostly they popped into place for me without any hassle like you had. We've just had different experiences here is all.

And, on this thread for Carlgustav, the point might be that it'll be a hell of a lot easier to check for leaks at the pipe joins BEFORE pulling the whole header off and looking at the gaskets. At least at the connector and slipon.  If they're bad, then they are quickly fixed. If they're good,  THEN I guess it's time to yank the header and see if something is leaking at the ports.

By the way, I got a good laugh at the "I'm an ATP" line. Old friend of mine -- also ATP, 25,000 flying hours, A&P, IA at the airport I worked at -- used to always tease us when we helped with maintenance.
"You know the four most dangerous things in aviation?"  He was a wonderfully self deprecating man.

2 hours ago, MooseMoose

By the way, I got a good laugh at the "I'm an ATP" line. 

Yeah, revealing any sort of qualification or expertise in today's online environment is to invite ridicule.  But I do it anyway (occasionally).

And no, I don't exactly know the particular joke you're referring to.  Maybe it's more of my "expertise" getting in the way of what I'm sure is both a very pithy and absolutely hilarious joke (In my Air Force time I was a safety officer and crash investigator so I actually do know what's dangerous).

So... I'm just throwing this out there. Forget kleenex and roach clips. If you're looking for leaks, bubble solution is your friend. A spray bottle with some dish soap and water will find leaks that won't stir a breeze.