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98 Gen 5 VFR runs rich (but all usual symptoms seem to function properly)


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Hello all! First of all. I love this forum. You guys are super knowledgeable and I hope one day I can stop asking questions and start answering them. Here is my issue at hand. 

 

I have a 98 Gen 5 VFR. No cats. As intended. At red lights or even in the garage when I start it up before I leave. I smell A LOT of exhaust fumes. I know this sounds silly. It's a motorcycle. But this is a bit excessive. Like I'm trying to not breath in my helmet. Lol. At highway speeds it goes away. But at standing. Or even when idling. I'm sure it can kill a small critter. Even my friends said the fumes are excessive. 

 

Here is what I did so far. All vac hoses on the throttle bodies have been replaced. The air filter is always changed when needed. The TPS has been dialed in at 0.5 at idle and 4.5 full throttle (it has to come off when I got the bike as it was cracked. I know Honda forbids you to do this. But I had no choice) I do have aftermarket headers and pipe from Black Widow. However. The problem was there with the OEM pipes as well. The fuel regulator has been changed aswell, new, OEM. With new hoses as well. So I don't think it's leaking. 

 

The injectors are also new. the fuel pump and fuel pump assembly is also new (fuel pump is NOT OEM. Just found a same size one on Amazon) there are no gas leaks. Or anything of that nature. Although I do smell gas escaping through the tank cap. (Probably needs replacing) but that's a dif smell than the exhaust fumes. 

 

I have tired PC5 maps and paid for a custom map. No change. So I'm actually selling it now if anyone is interested. 

 

There is no black smoke coming out the pipe. It's always clear.  With the whole fuel system seeming to work amazing. I just don't know what is going on. 

 

Do I just embrace this and am I overthinking? This is my 2nd bike. My first Fi bike though. 

 

Anywhere else I can look? Or things to test/check. I'm very hands on. But I do need guidance. 

 

The bike throws no codes. Most of the sensors have been replaced. 

 

Another bit. The engine has been swapped. But for the same engine. With less miles. Old engine has scarred cylinder walls from water damage. (Bike stood outside for a while until I found it and bought...and saved it. 14k miles it has. Now it has a bit over 20k. I have replaced almost everything. 

 

Any suggestions and ideas will be appreciated. Thank you! 

 

Pic from last night at the gas station. This thing is a beauty. 

PXL_20230501_074301417.PORTRAIT.jpg

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Check actual temps. No O2 sensors so if it's running cold the ECU will richen the mixture. Could be a temp sensor or stuck thermostat.

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45 minutes ago, MBrane said:

Check actual temps. No O2 sensors so if it's running cold the ECU will richen the mixture. Could be a temp sensor or stuck thermostat.

Hello! Thank you for the reply. Here is the thing.. I have changed the thermostat. OEM. The difference between the old and new were the same. Same smell. I have a brand new temp sensor. I did not install it yet. Is here a way to check if the old one is dying? Without....riping the TBs apart again. Haha

 

Also, question. I get the ECU dumps more fuel as the bike warms up. But even as my bike reaches temps of 200 and above.. fully warmed up. It still smells the same.

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I have a 98 VFR and 99 VFR and have several friends with early (98, 99) 5th gen VFRs.  The all seem to run well but have heavy exhaust smells.  I think this is due to the lack of a catalytic converters to clean up the exhaust.  The early 5th gens exhaust smell remind me of the cars of the 60's before cats.  Next time you are are around other pre-cat 5th gen VFRs see if yours is comparable in terms of exhaust smell.  If so, it is probable just the lack of catalytic converter in those years.  If you are getting around 40-42mpg and the bike is running well its probably normal.

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Measure vacuum in 5-way T that goes to MAP-sensor at idle and 3000rpms.

Measure MAP-sensor voltage output at idle and 3000rpms.

4 numbers total.

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Further to Danno's suggestion. Just for the hell of it!! Try swapping the MAP Sensor and Barro Sensor see if this has any effect, they are the same Part No.

 

Assume you have no active Fi Fault codes?

 

Perhaps a Starter Valve adjustment/check might help things. Note 5gen cylinder 2 to match 1, 3 is set to 20mmHg higher than 1 and 4 is set to 10mmHg higher than 1. (3 and 4 are set higher not dropped as per service manual)

 

How's your bike going post Earth Block mod?

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1 hour ago, VeeEffArah said:

How is the routing of the vent and drain tubes from the furl cap from bottom of tank?

You mean the two hoses from the gas tank? It's just two tubes so far. They don't even go down all the way. They're not connected to anything. I don't really know what it's supposed to look like. When I first got it. They were so crusty. I ripped them off. 😞 Ordered the two tubes from Partzilla. But don't really understand the set up. I think there is a 4 way involved. But I do not have it. You think that's it? 

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1 hour ago, joneill said:

I have a 98 VFR and 99 VFR and have several friends with early (98, 99) 5th gen VFRs.  The all seem to run well but have heavy exhaust smells.  I think this is due to the lack of a catalytic converters to clean up the exhaust.  The early 5th gens exhaust smell remind me of the cars of the 60's before cats.  Next time you are are around other pre-cat 5th gen VFRs see if yours is comparable in terms of exhaust smell.  If so, it is probable just the lack of catalytic converter in those years.  If you are getting around 40-42mpg and the bike is running well its probably normal.

I honestly think this may be it. But what sucks...is I don't know know anyone with 5th gens around my area. I don't think many ride them here in BK, NY. I did know someone with a 6th gen. It def smelled way better haha 

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7 minutes ago, Grum said:

Further to Danno's suggestion. Just for the hell of it!! Try swapping the MAP Sensor and Barro Sensor see if this has any effect, they are the same Part No.

Assume you have no active Fi Fault codes?

How's your bike going post Earth Block mod?

Grum! Hello. Great to have you here. Thanks for asking! The bike has been running amazing. Did highway and street miles today. No fi lights.  Nothing. So I decided to explore into the most persistent issue that I've had...this smell. Lol 

 

I'll def switch out the sensors and see what's up. But I don't really know how to measure vaccume at the 5 way joint. 

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16 minutes ago, Grum said:

Further to Danno's suggestion. Just for the hell of it!! Try swapping the MAP Sensor and Barro Sensor see if this has any effect, they are the same Part No.

Assume you have no active Fi Fault codes?

How's your bike going post Earth Block mod?

Oh and I didn't mention, there are the thankfully 0 fault codes. The bike seems to run great. Power wheelies in first gear. Mostly by accident. 😂

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I have a '98 and before I changed to an aftermarket pipe the strong unburned gas smell was minimal but there-but once I installed the new headers it became even stronger.  Like you I really notice it at a stoplight.  I know those behind me wish I had a catalytic converter on it!  The strong odor was there no matter if I was using a PC II or PCIII USB, no matter the map I tried.  I don't get particularly good gas mileage but don't ride in such a way that I expect that so I just accept that it's a gas hog and go about my business.

 

I hope you get yours sorted out-it is a beauty, as are all red ones!😉

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1 hour ago, Grum said:

Further to Danno's suggestion. Just for the hell of it!! Try swapping the MAP Sensor and Barro Sensor see if this has any effect, they are the same Part No.

 

Assume you have no active Fi Fault codes?

 

Perhaps a Starter Valve adjustment/check might help things. Note 5gen cylinder 2 to match 1, 3 is set to 20mmHg higher than 1 and 4 is set to 10mmHg higher than 1.

 

How's your bike going post Earth Block mod?

Hmm the valve adjustment... When I did that the first time I just had all of them match each other. I didn't know they differ in mmHg so much. Looks like I have a lot to check here. As always great advice. 

 

Coolant temp sensor.

Starter valve adjustment 

Measuring map sensor (I did however replace it before)  btw any advice on this? I'm not the best with the voltmeter. But I'm sure the manual will help. 

Finally, measuring vaccume in the 5 T. Which I still am confused about 🤔

 

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2 minutes ago, interceptor69 said:

I have a '98 and before I changed to an aftermarket pipe the strong unburned gas smell was minimal but there-but once I installed the new headers it became even stronger.  Like you I really notice it at a stoplight.  I know those behind me wish I had a catalytic converter on it!  The strong odor was there no matter if I was using a PC II or PCIII USB, no matter the map I tried.  I don't get particularly good gas mileage but don't ride in such a way that I expect that so I just accept that it's a gas hog and go about my business.

 

I hope you get yours sorted out-it is a beauty, as are all red ones!😉

Haha! It is a gas hog and I'm all about it. It's smiles for miles baby! I just wanna make sure I'm not killing the engine in any way 😂

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If you pull the spark plugs out, you should be able to roughly judge the fueling by looking at the colour of the insulator on the centre electrode. Black/sooty would be rich, white/light grey is lean and a slight tan colour is usually the Goldilocks Zone.

 

I agree that lacking a cat, the exhaust on the 5th gen is a bit smelly compared to bikes with cats fitted (I also have an MT-10 and ST1300).

 

Are you sure that the hose connecting to the pressure regulator is sealing well? The regulator uses the vacuum from the intake to reduce the fuel pressure under higher vacuum conditions. If that hose is leaking, then the injector pressure will be higher that desirable and more fuel is injected.

 

The two hoses referred to earlier from the tank are the air vent (skinny one) and the filler overflow (the fat one). Ideally you want the fat one to extend down under the bike so a fuel spill during filling doesn't run onto hot headers (but that could fix your rich-running very quickly!).  IIRC the skinny hose just needs to head downwards, its just there to allow fuel vapours to expand out or air to be sucked in as fuel is used. In CA that probably should go to a charcoal cannister if you still have one fitted ( that would be hose 1 in the diagram below).

 

The 5-way joint is also only relevant if you have the charcoal cannister fitted (CA). The rest of us have the vacuum hoses plugged into stubs on the airbox.

 

 

 vfr.thumb.jpg.8502c3aa47c43879628b578ac0caac7d.jpg

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10 minutes ago, Terry said:

If you pull the spark plugs out, you should be able to roughly judge the fueling by looking at the colour of the insulator on the centre electrode. Black/sooty would be rich, white/light grey is lean and a slight tan colour is usually the Goldilocks Zone.

 

I agree that lacking a cat, the exhaust on the 5th gen is a bit smelly compared to bikes with cats fitted (I also have an MT-10 and ST1300).

 

Are you sure that the hose connecting to the pressure regulator is sealing well? The regulator uses the vacuum from the intake to reduce the fuel pressure under higher vacuum conditions. If that hose is leaking, then the injector pressure will be higher that desirable and more fuel is injected.

 

The two hoses referred to earlier from the tank are the air vent (skinny one) and the filler overflow (the fat one). Ideally you want the fat one to extend down under the bike so a fuel spill during filling doesn't run onto hot headers (but that could fix your rich-running very quickly!).  IIRC the skinny hose just needs to head downwards, its just there to allow fuel vapours to expand out or air to be sucked in as fuel is used. In CA that probably should go to a charcoal cannister if you still have one fitted ( that would be hose 1 in the diagram below).

 

The 5-way joint is also only relevant if you have the charcoal cannister fitted (CA). The rest of us have the vacuum hoses plugged into stubs on the airbox.

 

 

 vfr.thumb.jpg.8502c3aa47c43879628b578ac0caac7d.jpg

Thank you for the explanation! Yes. I'm in NY. Don't have a Cali bike. Just the stubs you're talking about. Thank you for clearing that up. The fuel pressure reg hoses seem to be on really tight. I couldn't even get the damn thing off last time I tried to check. So I left it be. Haha

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Ok, no 5-way joint on your bike.

 

Use this vacuum-gauge to measure vacuum going to MAP sensor. Use T-fitting to tap into hose in-line with MAP sensor. It's primary sensor that ECU uses to calculate air-flow volume to determine how much fuel to inject.

https://www.amazon.com/Actron-CP7803-Vacuum-Pressure-Tester/dp/B0006V2BS2

At idle and low-loads, vacuum is high and ECU injects little petrol. At higher-loads and larger throttle-openings, vacuum is low and ECU injects more fuel.  

 

What often happens is vacuum hoses develops cracks and leaks, or get disconnected slightly when tank is removed and reinstalled. This vacuum leak lowers vacuum levels going to MAP sensor. It will read lower vacuum than actual and tricks ECU into thinking load is higher than actual. ECU then injects more petrol than required because it thinks load is higher. So you're cruising along with throttle barely open, but ECU thinks you're WOT!! 

 

Easier to just measure output voltage of sensor. Don't even have to take tank off. Then if numbers don't line up, you can crawl in there to measure vacuum and inspect for leaks

 

There's possibility that FPR has malfunctioned. Its job is to vary fuel-pressure according to load based on... intake vacuum! At low-loads and low fuel-demands, it lowers fuel-pressure. At high-loads it raises fuel-pressure. Leaks in vacuum hoses would cause it to send too-high pressure to fuel-rail. Only way to know for sure is to measure fuel-pressure in fuel-rail.

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4 hours ago, joneill said:

I have a 98 VFR and 99 VFR and have several friends with early (98, 99) 5th gen VFRs.  The all seem to run well but have heavy exhaust smells.  I think this is due to the lack of a catalytic converters to clean up the exhaust.  The early 5th gens exhaust smell remind me of the cars of the 60's before cats.  Next time you are are around other pre-cat 5th gen VFRs see if yours is comparable in terms of exhaust smell.  If so, it is probable just the lack of catalytic converter in those years.  If you are getting around 40-42mpg and the bike is running well its probably normal.

 

My experience is the same with 1998 and 1999 VFRs and they do tend to be a bit smelly.  Lack of a Cat and no O2 sensors means they're always open-loop.  The ECU has no real idea what is going on with engine output and is just throwing out a SWAG based on the sensors it does have.  If you're getting 38 MPG at 55-65 I wouldn't worry about it.

 

If you want a cleaner burning 5th gen get a 2000 or 2001.

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16 hours ago, DannoXYZ said:

Measure vacuum in 5-way T that goes to MAP-sensor at idle and 3000rpms.

Measure MAP-sensor voltage output at idle and 3000rpms.

4 numbers total.

Hey! So I did the Map sensor voltage output. And I think I have a problem. Let me just explain how I did everything. So first I checked for volts. To find the constant 5v line. Which I did. It was pink. Then I switched to continuity. At which point things started getting weird. Cause neither of the other 2 wires gave me anything. No beep. I went and got some needles to probe deeper. Nothing. Ok. 

 

I figured if I'm gonna see the volts at 3k rpm. The other two wires are the ones to go to. So I probed them from the back with two needles. Connected my voltmeter. And turned on bike. I it was around 2.3v. and when I revved it it honestly didn't have much. So either I did something wrong. Or something is faulty. Please advise. 😂

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15 hours ago, VicSev93 said:

Grum! Hello. Great to have you here. Thanks for asking! The bike has been running amazing. Did highway and street miles today. No fi lights.  Nothing. So I decided to explore into the most persistent issue that I've had...this smell. Lol 

 

I'll def switch out the sensors and see what's up. But I don't really know how to measure vaccume at the 5 way joint. 

Hello! So here is a video of how I tested the map for Volts at 3k rpm. Please advise if correct or if I'm dumb lol video cuts off. But at 3k rpm it went from 2.3 to 2.0

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2 hours ago, VicSev93 said:
2 hours ago, VicSev93 said:

Hey! So I did the Map sensor voltage output. And I think I have a problem. Let me just explain how I did everything. So first I checked for volts. To find the constant 5v line. Which I did. It was pink. Then I switched to continuity. At which point things started getting weird. Cause neither of the other 2 wires gave me anything. No beep. I went and got some needles to probe deeper. Nothing. Ok. 

 

I figured if I'm gonna see the volts at 3k rpm. The other two wires are the ones to go to. So I probed them from the back with two needles. Connected my voltmeter. And turned on bike. I it was around 2.3v. and when I revved it it honestly didn't have much. So either I did something wrong. Or something is faulty. Please advise. 😂

Hello! So here is a video of how I tested the map for Volts at 3k rpm. Please advise if correct or if I'm dumb lol video cuts off. But at 3k rpm it went from 2.3 to 2.0
 

Follow procedure in manual. You want to measure voltage on MAP-sensor output line to ECU. That's how ECU is getting data about environmental conditions. Measure voltage between lt.grn/yel signal wire using grn/org as ground.

 

1. key-ON, output = 2,7-3,1v

2. engine idling= 2,7v max

 

Do same measurements with BARO sensor, output-voltage on lg.grn/blk, grn/org as ground.

Graph output-voltage measurements at various RPMs and it should fall into these ranges (need to translate altitude into absolute-pressure/vacuum).
uc?export=download&id=1o_ax4iwo6heE0zds3

 

vacuum in intake at idle should be 200-250mmHg.

fuel-pressure at idle should be 36psi

fuel-pressure at WOT should be 45-50psi.

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1 hour ago, DannoXYZ said:

Follow procedure in manual. You want to measure voltage on MAP-sensor output line to ECU. That's how ECU is getting data about environmental conditions. Measure voltage between lt.grn/yel signal wire using grn/org as ground.

 

1. key-ON, output = 2,7-3,1v

2. engine idling= 2,7v max

 

Do same measurements with BARO sensor, output-voltage on lg.grn/blk, grn/org as ground.

Graph output-voltage measurements at various RPMs and it should fall into these ranges (need to translate altitude into absolute-pressure/vacuum).
uc?export=download&id=1o_ax4iwo6heE0zds3

 

vacuum in intake at idle should be 200-250mmHg.

fuel-pressure at idle should be 36psi

fuel-pressure at WOT should be 45-50psi.

So it does fall within the key ON at 2.8. but anyone idling it's 2.3v. am I good to go then? I will check the rest tonight. Thank you. 

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20 hours ago, DannoXYZ said:

Ok, no 5-way joint on your bike.

 

Use this vacuum-gauge to measure vacuum going to MAP sensor. Use T-fitting to tap into hose in-line with MAP sensor. It's primary sensor that ECU uses to calculate air-flow volume to determine how much fuel to inject.

https://www.amazon.com/Actron-CP7803-Vacuum-Pressure-Tester/dp/B0006V2BS2

At idle and low-loads, vacuum is high and ECU injects little petrol. At higher-loads and larger throttle-openings, vacuum is low and ECU injects more fuel.  

 

What often happens is vacuum hoses develops cracks and leaks, or get disconnected slightly when tank is removed and reinstalled. This vacuum leak lowers vacuum levels going to MAP sensor. It will read lower vacuum than actual and tricks ECU into thinking load is higher than actual. ECU then injects more petrol than required because it thinks load is higher. So you're cruising along with throttle barely open, but ECU thinks you're WOT!! 

 

Easier to just measure output voltage of sensor. Don't even have to take tank off. Then if numbers don't line up, you can crawl in there to measure vacuum and inspect for leaks

 

There's possibility that FPR has malfunctioned. Its job is to vary fuel-pressure according to load based on... intake vacuum! At low-loads and low fuel-demands, it lowers fuel-pressure. At high-loads it raises fuel-pressure. Leaks in vacuum hoses would cause it to send too-high pressure to fuel-rail. Only way to know for sure is to measure fuel-pressure in fuel-rail.

I have ordered the vaccume pressure gauge to connect to the hose from the map sensor and document the pressure I'm getting there. 

 

For the fuel rail...how do I even measure it? I know cars have a valve for a gauge to plug in..but my bike definitely does not... 😂

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32 minutes ago, VicSev93 said:

I have ordered the vaccume pressure gauge to connect to the hose from the map sensor and document the pressure I'm getting there. 

 

For the fuel rail...how do I even measure it? I know cars have a valve for a gauge to plug in..but my bike definitely does not... 😂

Mr Honda says to do the fuel pressure check at the fuel pump banjo bolt on the underside of the fuel tank. However...that might be worth doing if the fuel flow/pressure was low. Can't see any point if the pressure is suspected to be high. The fuel pump should always kick out more pressure than needed, hence the function of the regulator downstream. 

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2 minutes ago, Terry said:

Mr Honda says to do the fuel pressure check at the fuel pump banjo bolt on the underside of the fuel tank. However...that might be worth doing if the fuel flow/pressure was low. Can't see any point if the pressure is suspected to be high. The fuel pump should always kick out more pressure than needed, hence the function of the regulator downstream. 

Is it possible ... That the FPR is not able to regulate the fuel and send too much of it down the rails? Do I remove the vaccume hose from the FPR and see if it leaks? 

 

Btw thank you so much! 

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