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5th gen bad mileage/rich running -- opinions on what to check


MooseMoose

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My bike has always run rich since I bought it. Lots of pops and bangs from unburnt fuel on decel when quickly rolling off after acceleration, etc.  It sounded like a hooligan bike from the days of carbs, actually, which was kind of fun, but really annoying at the same time.

 

A power commander fixed that right up, no more popping or whatever. Now I have a Rapid bike system in there.  However, it still has issues.

 

I got it with 20K miles and have put 8K on it since. I have done a lot of maintenance and restoration during the last 2 years, but it still gets crap mileage and the controller really wants to lean it off.  So none of my maintenance has worked.

 

I'll list symptoms and see if anyone can come up with ideas for what to check next.

 

1. Poor mileage.

2. Symptoms of running rich at low throttle mid RPMs (like 5K) -- wet sound with little pops, a touch of fuel smell in the exhaust, etc. 

3. Rapid bike wants to lean the bike off a LOT at lower throttle

4. If I let the Rapid bike do large corrections it eventually maxes them out and the bike runs worse -- it gets rougher and more inconsistent

5. Power is good, especially as the RPMs come up and the throttle opening increases, and the engine runs well

6. Cooling is normal -- on a 90 degree day I'll see 230s climbing a mountain behind cars, on a cool evening  in free air I'll be pegged at 177-181, which tells me where my thermostat opens, and in normal use in open air it'll run between 200 and 220. depending on ambient and how hard I'm running.

 

 

What I've checked and fixed:

* Had the injectors cleaned at RC Injection. They flow tested them to 1%

* New fuel regulator

* New plugs

* Running a rapidbike (which makes it a LOT nicer in most cases, but doesn't change the mileage one iota)

* new cooling hoses, thermostat (the old one tests fine, too), etc.

* Obviously starter valve sync. Many times, every time I R&R the throttle body to try these things out.

* Chain, sprockets

* Redid the brakes (new SS lines, disks, pads, the rear wheel isn't dragging  when it's on the center stand and the pistons moved when I checked)

 

No difference in mileage from any of these. Like I said, lots of smooth  power up top, but it just isn't right in the midrange and mileage remains less than 30 no matter how gentle  I am on it. I mean, it's a big difference getting 25-28 when I expect 35 or more.

 

I'm kind of shooting in the dark now at what might be causing it. Thoughts:

 

- Aftermarket exhaust (the Delkovic system) ? 

- Could a fuel injector still be bad?  Like it isn't closing? In my imagination that would mean 3 of the 4 cylinders are going lean and one staying rich, but I don't know how injectors work well enough to know if that idea is poppycock.

- Could a fuel filter cause this? (I'd think that would make it leaner, not richer)

- Could valves be misadjusted enough to cause this?

- Could it be an intermittent brake dragging problem?

- Could it be something else entirely?

 

Any ideas and tips on how to diagnose them  are greatly appreciated.

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Would it help to disconnect the programming effects, put a stock can on and establish a non-altered base line? That may eliminate a number of questions/potentials. At 5000 rpm steady highway riding I frequently have had 50+ mpg. 

 

My mileage improved 10%+ when I took off the PCII and StainTune can that came with my 11,000 mile (58,000 mi. now) current-rider 2001. :wub::wheel::3:

 

I've also experienced a dragging rear brake. It heated up the rear brake works to make them inoperable. And in a palm-to-the forehead moments, when breaking in new boots, I've found myself accidentally ride the rear pedal, wondering why the heck this isn't responding to the throttle. YMMV  

 

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A couple of thoughts.... Are you running a clean air filter? And are you running Premium Fuel? If so try running on the Octane rating in your owners manual which I think for America in 86 minimum. It could be that if running Premium Fuel which is of lower volatility just might be causing the rich situation. There's no benefit to be made by running Premium Fuels on a VFR.

 

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8 minutes ago, Grum said:

A couple of thoughts.... Are you running a clean air filter? And are you running Premium Fuel? If so try running on the Octane rating in your owners manual which I think for America in 86 minimum. It could be that if running Premium Fuel which is of lower volatility just might be causing the rich situation. There's no benefit to be made by running Premium Fuels on a VFR.

 

That reminds me (thanks Grum), the machine I'm talking about also came with the typical aftermarket air filter. Much better breathing with OEM. And may have contributed to the marked increase in mpg.

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I aslo have the Delkevic system with a Staintune open muffler on my 2001.

I don't think the pipes are that good for milage or performance.

I was running off the internet maps on my PCIIIUSB, and while it went well, my milage was bad.

Around 300km per tank, most of my rides are spirited and I don't do traffic or commute.

Since then I started running a very lean map from an old PCII, it varies around 15% to 20% leaner across the whole range.

I can now lift the front wheel up without clutch in first, runs really good accross the whole range, and I'm back to getting over 350km per tank.

I know a custom map is the way to go, but it's too expensive here, I've been quoted from AU$400 to AU$750.

I have O2 sensor eliminators, PAIR valves removed, using coil on plugs and about 15kg less weight than stock.

If your bike is a California bike, I think it is different to all the rest of the world 2001 models so not sure how the mapping works

 

 

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Excellent ideas everyone. Let me try to answer questions in one post instead of individually. From last to first:

 

@VFROZ

1. Bike is not a California bike. It lived in the midwest for the first 15 years of its life

.  Guy I bought it from shipped it out here a few years ago.

 

2. For Power Commander stuff -- I don't have a PCIII in there anymore. Not for 18 months.  I have a Rabidbike Racing module with its own sensor. This is near-real-time fuel controlling via the sensor. This is part of how I know the midrange is super rich.

2.a. I have O2 elimitators in there. I tried it without on the off chance that it was running rich because it wasn't seeing the proper sensor value and went into an over-rich default mode, but it was just as bad for rich, but worse oerall.  Without them it is unridable. Like surges horribly when it goes into cruise mode then comes out. Since the fuel controller tries to to compensate for the changing fueling in the ECU it eventually gets the midrange so fucked up that it is horrible to ride.  With the resistors in it is predictable.

 

What's happening with the Rapidbike will try to lean the midrange out. If I give it a trim value of 10, betweeen 4500 and 6000 it might trim it at lower throttle opening all the way to max lean. At 5000 - 5500 it'll sometimes trim it literally to the max trying to lean it off for most throttle settings, so I'll see 10 all the way across.  If I cap it at 4 or 5 it will go to 5, but run smoother with fewer of the rich-bike symptoms.

 

I've also tried trimming the whole thing, and tried shooting for leaner ratios -- everything from 13.1 to 14. When i go leaner than low 13s it will just peg more of the adjustments to max and be unable to reach my lean target and the bike runs less good.

 

3. I lifted a wheel last weekend with just power. It isn't weak, it's just really wet and I can't make it leaner even if I try.

 

4 hours ago, Grum said:

A couple of thoughts.... Are you running a clean air filter? And are you running Premium Fuel? If so try running on the Octane rating in your owners manual which I think for America in 86 minimum. It could be that if running Premium Fuel which is of lower volatility just might be causing the rich situation. There's no benefit to be made by running Premium Fuels on a VFR.

 

 

4. I run premium fuel.  I got some knocking with my ignition map so I had to. I zeroed the ignition map (no advance) with no benefit to mileage. But I still run the premium fuel.

 

That said -- Rapidbike. If it's seeing unburnt fuel it should lean it out. But when it tries to lean it out a lot the bike runs rough.

 

5. I had a K&N in there (came with the bike)  and I cleaned it. No difference. I jammed a brand new Pipercross in there which should let more air through than the K&N. No difference.

 

5 hours ago, MaxSwell said:

Would it help to disconnect the programming effects, put a stock can on and establish a non-altered base line? That may eliminate a number of questions/potentials. At 5000 rpm steady highway riding I frequently have had 50+ mpg. 

 

My mileage improved 10%+ when I took off the PCII and StainTune can that came with my 11,000 mile (58,000 mi. now) current-rider 2001. :wub::wheel::3:

 

I've also experienced a dragging rear brake. It heated up the rear brake works to make them inoperable. And in a palm-to-the forehead moments, when breaking in new boots, I've found myself accidentally ride the rear pedal, wondering why the heck this isn't responding to the throttle. YMMV  

 

 

 

6. I can't put the stock can back on. These are a full system including headers so the stock can won't connect up. Maybe they're partly to blame, but I should be able to lean it out to match, shouldn't I? Maybe I could try with and without the silencer baffle, to see if there's a difference there. It has to change the backpressure, I'd assume.

 

7. I'm CERTAIN I'm not dragging my boot on the brake pedal!   I ride on my toes, and I've been riding a long long time.  That doesn't mean there isn't some intermittent problem, but every time it goes on the centerstand I can spin the rear wheel by hand but my mileage is *consistently* very poor, around town or when I'm moving, every tank.

 

I'm not expecting to get the best mileage running a hot map, but I got the same crap mileage when I first got it, before I tried a fuel controller. That was stock fueling, no O2 eliminators, no PCII or Rapidbike, and it got less than 30 and ran so rich you could sometimes smell the fuel in the exhaust.

 

The more I write about it, the more I'm worried that when it makes it super lean it runs badly.  I have to strip a bunch of plastic off, so maybe I'll pull the plugs and see if they all look the same. That might lead me to a bad injector.

 

 

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1 hour ago, MooseMoose said:

The more I write about it, the more I'm worried that when it makes it super lean it runs badly.  I have to strip a bunch of plastic off, so maybe I'll pull the plugs and see if they all look the same. That might lead me to a bad injector.

Why would you suspect a bad injector when you've had them serviced and are flow tested to within 1%.

What about the PAIR system, if this is still operational on your bike could this be screwing with your tuning system, cold air injected into the exhaust ports would tell fuelling to richen up would it not?

 

Sorry but it's a bit out of my league, never messed with a PC or Rapidbike system. All I know is running too lean or rich downgrades performance however get it too lean and it could be destructive.

Perhaps there might be some good expert advice and setting up with any of the Dyno specialists out there.

Good luck.

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Basic thought:  First, you're not getting any FI light codes. 

 

This means the PGM-FI ECM has proper connections with all of the sensors.  It also indicates that the sensor inputs the ECM is receiving are within the generally-expected range of operation for each parameter.  This is good news but it doesn't rule out a situation where one or more of the input elements of the FI system might be operating in a strange way and is producing inaccurate readings (Throttle Position Sensor, Coolant Temp sensor, Intake Air Temp sensor,  Barometric Pressure sensor, Intake Manifold Negative Pressure sensor, Engine Revolution Speed sensor, Camshaft Pulse sensor).

 

If you read the VFR800 Service Manual Chapter 21 "Technical Features" Page 21-11, you'll learn that the VFR800's PGM-FI runs (fuels) the engine in 2 different modes depending on how far the rider twists the grip to open the throttle plates (moving the Throttle Position sensor).  At lower throttle openings the controlling parameter in the fueling computations is the Intake Manifold Negative Pressure sensor.  At wider throttle openings the controlling parameter is the Throttle Position sensor.

 

Your description of your VFR's behavior sounds like the ECM is having trouble determining proper fueling while the engine is in the part of the operating range where the Intake Manifold Negative Pressure sensor is used as the controlling parameter.  You seem to indicate that the bike pulls powerfully (as it should) when the RPMs are high and you're at wider throttle opening (on the throttle hard), so this suggests that the engine is fueling properly when the ECM is using the Throttle Position sensor as the controlling parameter.

 

 

 

 

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1 hour ago, GreginDenver said:

Basic thought:  First, you're not getting any FI light codes. 

 

This means the PGM-FI ECM has proper connections with all of the sensors.  It also indicates that the sensor inputs the ECM is receiving are within the generally-expected range of operation for each parameter.  This is good news but it doesn't rule out a situation where one or more of the input elements of the FI system might be operating in a strange way and is producing inaccurate readings (Throttle Position Sensor, Coolant Temp sensor, Intake Air Temp sensor,  Barometric Pressure sensor, Intake Manifold Negative Pressure sensor, Engine Revolution Speed sensor, Camshaft Pulse sensor).

 

If you read the VFR800 Service Manual Chapter 21 "Technical Features" Page 21-11, you'll learn that the VFR800's PGM-FI runs (fuels) the engine in 2 different modes depending on how far the rider twists the grip to open the throttle plates (moving the Throttle Position sensor).  At lower throttle openings the controlling parameter in the fueling computations is the Intake Manifold Negative Pressure sensor.  At wider throttle openings the controlling parameter is the Throttle Position sensor.

 

Your description of your VFR's behavior sounds like the ECM is having trouble determining proper fueling while the engine is in the part of the operating range where the Intake Manifold Negative Pressure sensor is used as the controlling parameter.  You seem to indicate that the bike pulls powerfully (as it should) when the RPMs are high and you're at wider throttle opening (on the throttle hard), so this suggests that the engine is fueling properly when the ECM is using the Throttle Position sensor as the controlling parameter.

 

 

 

 

That is the most cogent explanation of the VFRs PGM-FI systems I've come across. Good work GID.

Thank you. 

 

P.S. A high school shop teacher: "When all else fails, RTFM!":fing02:

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On 8/31/2018 at 11:49 PM, Grum said:

Why would you suspect a bad injector when you've had them serviced and are flow tested to within 1%.

 

Two things make me ask the question.

 

1. Desperation. I'm literally trying to consider everything, even if it is remote. I'm literally ASKING if it is possible for this to happen, not saying I think it's the #1 possibility.

 

My logic is that the flow test RC Injection does is to open them up, run them at a certain fuel pressure for a certain period of time, then measure how much fuel has passed through them into the measuring tubes.   I don't think they test like pulsing the injectors multiple times and seeing how close the flow matches. And I don't know how injectors work well enough to know if it is possible for one to stick open -- like sometimes be slower closing than others when the voltage is dropped back to zero.  Thus the question.

 

2. When the fuel is leaned out the bike runs poorly. Like it is rough. The million to one shot is that one of the injectors isn't always closing quickly. 

 

Again, I  am reaching with this and genuinely asking if it is even a possibility.

 

Quote

What about the PAIR system, if this is still operational on your bike could this be screwing with your tuning system, cold air injected into the exhaust ports would tell fuelling to richen up would it not? 

 

 

PAIR is disabled. Removed, with plates over the holes. At some point I pulled the plates, inspected, and reset them to make SURE they weren't leaking.

 

This was a GREAT mod, but the way. It immediately benefited my idle smoothness, so I think they were a touch leaky before I did it. But they didn't help the problem I'm having with richness.

 

I think Greg has me on a different track, but I wanted to respond to your questions, too. Thank you for the suggestions and helping me think it through! 

 

On 9/1/2018 at 3:07 AM, VFROZ said:

What O2 sensors are you using for the Rapidbike? 

 

 

The Bosch sensor that came with it and the MyTuning module (the thing that does tuning in real time). The stock sensors are not connected at the moment, but I ran them without the MyTuning in the past with similar results.

 

 

On 9/1/2018 at 8:30 AM, GreginDenver said:

Basic thought:  First, you're not getting any FI light codes. 

 

No. No codes.

 

 

 

 

Quote

This means the PGM-FI ECM has proper connections with all of the sensors.  It also indicates that the sensor inputs the ECM is receiving are within the generally-expected range of operation for each parameter.  This is good news but it doesn't rule out a situation where one or more of the input elements of the FI system might be operating in a strange way and is producing inaccurate readings (Throttle Position Sensor, Coolant Temp sensor, Intake Air Temp sensor,  Barometric Pressure sensor, Intake Manifold Negative Pressure sensor, Engine Revolution Speed sensor, Camshaft Pulse sensor).

 

If you read the VFR800 Service Manual Chapter 21 "Technical Features" Page 21-11, you'll learn that the VFR800's PGM-FI runs (fuels) the engine in 2 different modes depending on how far the rider twists the grip to open the throttle plates (moving the Throttle Position sensor).  At lower throttle openings the controlling parameter in the fueling computations is the Intake Manifold Negative Pressure sensor.  At wider throttle openings the controlling parameter is the Throttle Position sensor.

 

Your description of your VFR's behavior sounds like the ECM is having trouble determining proper fueling while the engine is in the part of the operating range where the Intake Manifold Negative Pressure sensor is used as the controlling parameter.  You seem to indicate that the bike pulls powerfully (as it should) when the RPMs are high and you're at wider throttle opening (on the throttle hard), so this suggests that the engine is fueling properly when the ECM is using the Throttle Position sensor as the controlling parameter.

 

 

 

 

 

 

Yes, the problem mostly happens at low throttle. Like cruising around at 5-10% throttle and 5K RPM, 50mph down a flat road.   It pulls great when you're riding harder. This very well could be it! Great call.

 

I SWEAR I read this in the manual at some point, and totally missed the two throttle modes! 

 

That said, the MAP sensor is friggen EXPENSIVE!    I'll troubleshoot it though. Maybe it isn't enough out of range to throw an error, but still  far enough off to make the bike super rich at 5% throttle. My truck had an intermittent issue with a MAP and cleaning it bought me 15000 miles until it died completely, so fingers crossed. No matter what, if cleaning or a gently used part changes this behavior I've got the most likely suspect.

 

Greg, your maintenance pics and suggestions have been a help to me since the day I bought this bike. I lurk more than I post, but I am VERY appreciative. If you're ever in San Diego I owe you the beverage of your choice.

 

 

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On 5 September 2018 at 12:05 PM, MooseMoose said:

That said, the MAP sensor is friggen EXPENSIVE!    I'll troubleshoot it though. Maybe it isn't enough out of range to throw an error, but still  far enough off to make the bike super rich at 5% throttle. My truck had an intermittent issue with a MAP and cleaning it bought me 15000 miles until it died completely, so fingers crossed. No matter what, if cleaning or a gently used part changes this behavior I've got the most likely suspect.

Hi Moose.

If you're suspecting the MAP sensor. What is the state of all the Vaccum hoses to the 5 way junction and to the MAP sensor itself, could you have a crack in any of these, causing a vacuum leak and messing up the MAP sensor output, perhaps not to the point of flagging an Fi fault code. Just a thought!

 

POST EDIT - Sorry was thinking of the 6gen MAP sensor configuration not the same arrangement for the 5gen.

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16 hours ago, MooseMoose said:

 

 

Greg, your maintenance pics and suggestions have been a help to me since the day I bought this bike. I lurk more than I post, but I am VERY appreciative. If you're ever in San Diego I owe you the beverage of your choice.

 

 

 

I'm in San Diego all the time (I'm a Southwest Airlines pilot).

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6 hours ago, Grum said:

Hi Moose.

If you're suspecting the MAP sensor. What is the state of all the Vaccum hoses to the 5 way junction and to the MAP sensor itself, could you have a crack in any of these, causing a vacuum leak and messing up the MAP sensor output, perhaps not to the point of flagging an Fi fault code. Just a thought! 

 

I don't know! Thanks for the pointer,  it'll be the first place I look.  I will find out when I get in there.

 

Problem with older bikes like this. They look all pretty, but they're still 18 years old and hoses and seals can be crusty.

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On 9/5/2018 at 3:05 AM, MooseMoose said:

That said, the MAP sensor is friggen EXPENSIVE!    I'll troubleshoot it though. Maybe it isn't enough out of range to throw an error, but still  far enough off to make the bike super rich at 5% throttle.

 

I believe the MAP and Barometric Pressure sensors are the same  (SENSOR ASSY., MAP part number 37830-P13-003)

Maybe try switching them over and see if that makes any difference to the way the engine runs?

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12 hours ago, MooseMoose said:

 

I don't know! Thanks for the pointer,  it'll be the first place I look.  I will find out when I get in there.

 

Problem with older bikes like this. They look all pretty, but they're still 18 years old and hoses and seals can be crusty.

 

Hey Moose. Sorry I was wrongly referring to the MAP sensor configuration of the 6gen. Don't think the 5gen has the 5way Vaccum junction. 

Good luck with your issues.

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There is only ONE thing that determines your fueling at low RPM/part throttle:  That's the MAP sensor.  The expensive piece that reads the vacuum from all 4 of your throttle bodies.  Since you didn't mention a high idle, you probably don't have a vacuum leak.  You also mentioned Coolant temps are normal so your coolant temp sensor is working.  That leaves a possible faulty MAP sensor.

 

Another area, which could be a Moon shot for you--

My 2007 VFR800 normally would get 31-33 mpg in mixed riding in recent times.  Even after a thorough tune up.  The best it got was 35 mpg when easy on the throttle.  I remembered before it normally got 35 mpg at worse and 41 mpg at best (with PC5 and O2 Eliminated).  I also noticed throttle response at part throttle wasn't as crisp as it used to be.  Then my  only-1-year old water pump (I replaced it because the original one leaked also) started to leak so I replaced it with a new one again.  I noticed that the leaking water pump impeller was very difficult to spin by hand compared to the new water pump.  Ok I figured failed water pump seal caused the bearings to go.  With the new water pump AND Pro Honda Coolant in place, my bike's fuel efficiency gained....went back to its original 35-41 mpg.  I even saw almost 43 mpg recently.  Even the throttle response and overall engine smoothness improved.

 

So it appears the old, failing water pump with the bad seal (and probably bearing) was dragging the engine enough to cause poor gas mileage because it was dragging down the engine.

 

I also realized after doing some more research that Pro Honda Coolant is one of the few coolants that does NOT use Silica Inhibitors for Aluminum engines.  The Silica Inhibitors used by most aftermarket coolant makers are known to cause premature water pump seal failures.  Since I used aftermarket Maxima Coolant for my VFR, that probably caused my previous two water pump seals to fail.  

 

If your engine isn't being physically dragged down by a failing water pump, brakes, or something, that leaves only the electronic path that controls your fuel injectors to cause the overly rich condition.  So if your MAP sensor checks out, that leaves only the ECM/RB controller.  I'd even check your new Fuel Pressure Regulator.  There really aren't that many things that control your injectors' flow.  

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Is there some issue with the fuel pressure regulator? Any chance the previous owner swapped it out with a different model? I don't know how you could tell by looking. Worth $60 to just throw a new one at it? (Price from Ron Ayers)

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On 9/6/2018 at 1:34 PM, KevCarver said:

Is there some issue with the fuel pressure regulator? Any chance the previous owner swapped it out with a different model? I don't know how you could tell by looking. Worth $60 to just throw a new one at it? (Price from Ron Ayers)

 

I have two here. A used good one off a wrecked 45mpg bike, and a brandy spankin' new one (which is on there now)  and between the three regulators absolutely nothing changed in the slightest.  I'm pretty certain on that front.

 

On 9/6/2018 at 12:50 PM, Rogue_Biker said:

So it appears the old, failing water pump with the bad seal (and probably bearing) was dragging the engine enough to cause poor gas mileage because it was dragging down the engine.

 

I also realized after doing some more research that Pro Honda Coolant is one of the few coolants that does NOT use Silica Inhibitors for Aluminum engines.  The Silica Inhibitors used by most aftermarket coolant makers are known to cause premature water pump seal failures.  Since I used aftermarket Maxima Coolant for my VFR, that probably caused my previous two water pump seals to fail.  

 

If your engine isn't being physically dragged down by a failing water pump, brakes, or something, that leaves only the electronic path that controls your fuel injectors to cause the overly rich condition.  So if your MAP sensor checks out, that leaves only the ECM/RB controller.  I'd even check your new Fuel Pressure Regulator.  There really aren't that many things that control your injectors' flow.  

 

 

Water pump!  That's just bananas. But, I can see it happening of the bearings are dragging. Those things should spin with no more drag than the water pressure itself causes.

 

I replaced the green fluid when I got the bike with red stuff (toyota) which is identical spec to the honda blue stuff. It's actually Zerex, but it is a silicate free  borate free with phosphate inhibitors just like Honda's Type2 and Toyota's spec for that matter.   That said, I've got this in the back of my mind for when I get to the sensor. 

 

I've been out of town for work so I haven't gotten in there yet, but I'll report back when I do. 

 

Thanks again everyone. The font of experience here is really cool.

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57 minutes ago, MooseMoose said:

I have two here. A used good one off a wrecked 45mpg bike, and a brandy spankin' new one (which is on there now)  and between the three regulators absolutely nothing changed in the slightest.  I'm pretty certain on that front.

 

Dangit!

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It's a MAP sensor. I went in there to clean everything and, on a whim, rerean the diagnostic. Blink blink.

 

So, it was probably on the way out when I did this test before but still tested ok. That was more than 5000 miles ago. Now it definitely tests bad.

 

I have  one on the way.   Good call @GreginDenver

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6 hours ago, MooseMoose said:

It's a MAP sensor. I went in there to clean everything and, on a whim, rerean the diagnostic. Blink blink.

 

So, it was probably on the way out when I did this test before but still tested ok. That was more than 5000 miles ago. Now it definitely tests bad.

 

I have  one on the way.   Good call @GreginDenver

 

Makes you wonder how common this situation is.  How many 5th Gens have a MAP sensor that isn't operating at 100%?   And this would include any other VFR Gens that use the same model of MAP sensor.  So maybe the 5th Gen VFR's MAP sensor slowly goes bad during an 18 to 20 year lifespan (which is where our 5th Gens are now).   Based on your experience it appears the MAP can deteriorate and reach a point where it causes a noticeable fueling problem some time before the PGM-FI system senses it strongly enough to blink a code. 

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I agree Greg, I've been watching this thread to see where it goes as I've had a rich running problem for a while.

Not bad, but noticable and could find no fault.

I'll have to have a closer look at my MAP.

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So, update here.

 

To clarify, right now I am getting 2 flashes -- MAP sensor bad -- when I do diagnostic. This didn't happen at 22K miles when I had a different fault and did diagnostic, but now (28K) it does, all the time, even after clearing the codes.

 

1. I  got a used map sensor off a supposedly good-running 2000.

2. I installed the "new" sensor and have an identical error

3. I started walking the troubleshooting guide, but I ran out of time. However, I think I'm getting reasonable voltage at the connector, and I have a fresh battery and cleaned every connection, so...

 

4.   My next step is to check the vacuum source.   

 

Dammit.

 

I ran out of light, but maybe tomorrow I'll put a gauge on the vacuum and see if it isn't right. But at this point it's either a vacuum issue, or it is a second faulty sensor, which is entirely possible because, let's face it, buying a 20 year old sensor off a wrecked bike on ebay for $30 is a gamble.

 

 

 

I dread the results of the vacuum test. But my current best guess is that's the real culprit. It was possibly intermittently bad before and I've made it worse during the maintenance I did on the injectors and replacing the hoses.  Weak vacuum means I have to  yank the throttle body.  Again.

 

I've had that damned throttle body off so many times already it seems almost hilarious that I once preemptively replaced all my hoses and o rings because "That way I'll never have to take the throttle body off again!" But, in the same vein, if I show weak vacuum I'll buy a roll of hose and replace literally every single piece of vacuum line under the throttle body.

 

More updates when I know more.

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  • 1 month later...
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Hey everyone -- I'm still working on this but, alas, I've had very few free days in the last month.  The days I have had free have coincided with really nice weather and I went for rides.

 

I have determined that I have vacuum at the sensor, but I'm still getting a code. What's happening is that it isn't  correct (or enough) vacuum, so I'm throwing a code and going into "default" mode. The underside of the throttle body has been beaten up more than once as I replaced hoses and injectors, so I'm assuming I have a leaky line and made an intermittent problem worse, which is why I didn't get a code when I first tested this 18 months ago but do now.

 

My plan is to replumb all vacuum lines under the throttlebody. When this tank is low enough to take off without spilling I'll get under there. I ordered hoses from the internets and have them in hand.

 

As for ordering hoses, Partzilla doesn't have the vacuum lines they say they have. I mean the funky shaped ones that I was hoping to get Honda stock, knowing they'll fit without kinks. I guess they're not made anymore so you just have to deal with bulk hoses. After a two week runaround where they sent me a $3 screw and charged me $8 shipping for it, but didn't send me the part of the order I actually needed, I found bulk vacuum hose elsewhere.  

 

Also, when ordering bulk hose from the internets, you have to watch the outside diameter. My first order had an OD of .130 where the stock hoses are 100. It makes a difference! The extra bulk worried me, so I ordered from a second source and the outside is pretty close to the hose that's on there right now. I'm sure it will work nicely.

 

The brand that I got that's a match in size is from NXS Motorsports. I got red and blue, because I want the underside of the throttle body to be really pretty.

 

The brand that's too fat is NXS. Avoid this brand for this application. It's good hose, so I'd gladly use it on my truck or some place where size is not an issue, but I don't want to worry about it getting smashed against the thermostat housing or pinched trying to route it out to the sensors. Avoid this hose for your VFR.

 

So, I'll be pulling it in a few days. I'll try to remember to take pics.

 

 

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