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

[DannoXYZ]

44 minutes ago, VicSev93 said:

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! 

That is just one failure mode of FPR. But it can also fail and not leak. Resulting in too high fuel-pressure. A test of FPR is to take 2-measurements of fuel-pressure in rail. One with vacuum hose disconnected. And one with it connected. Difference should be proportional to vacuum applied.

 

You can get tester with Autozone's free rental programme. Just put down deposit for kit, then get it back when returning kit.

[DannoXYZ]

1 hour 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. 

Pressure only exists between pump and FPR. Doesn't matter where you measure it, pressure will be same at any point in between.

 

Pump actually doesn't generate much pressure on its own, just flow volume. It's FPR at other end of rail that creates restriction. It's pump trying to force fuel through this restriction that backs up and creates pressure in rail. More restrictive the FPR's setting, the more pressure is created between pump and FPR (rail). 

 

It's like flowing garden hose, very little pressure. Until you stick thumb over end to restrict flow. Then flow is backed-up hose and generates pressure. The tighter you squeeze opening, the higher the pressure.

[Terry]

1 hour ago, VicSev93 said:

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! 

Yes absolutely possible. The vacuum from the intake port reduces the fuel pressure delivered to the rails. If the vacuum hose fails, then the FPR will continue to deliver more fuel than needed when the intake vacuum rises. The other possible failure would be a diaphragm failure within the FPR, and that can lead to fuel leakge directly into the vacuum hose and to the cylinder, and I expect the regulating of pressure wll be compromised as well. 

 

How do your spark plugs look?

[Terry]

48 minutes ago, DannoXYZ said:

Pressure only exists between pump and FPR. Doesn't matter where you measure it, pressure will be same at any point in between.

 

Pump actually doesn't generate much pressure on its own, just flow volume. It's FPR at other end of rail that creates restriction. It's pump trying to force fuel through this restriction that backs up and creates pressure in rail. More restrictive the FPR's setting, the more pressure is created between pump and FPR (rail). 

 

It's like flowing garden hose, very little pressure. Until you stick thumb over end to restrict flow. Then flow is backed-up hose and generates pressure. The tighter you squeeze opening, the higher the pressure.

Not arguing with any of that. I may not have expressed my thought clearly, but given the symptom is (perhaps) rich running due to (perhaps) excessive fuel rail pressure, then checking the fuel pump pressure would seem to be a bit pointless. It seems very unlikely that a stock pump would somehow deliver more flow/pressure than it was meant to, and in case a properly working FPR should control that. If the engine was running badly as a result of LOW fuel flow/pressure then I would absolutely check the pump. 

[gropula]

I've been battling a similar issue with my '02 VTEC. Always running rich and spewing soot out the exhaust, horrible gas mileage. Almost getting better mileage when riding like a maniac rather civilised riding. I've replaced FPR, sparkplugs, injectors (non-OEM '07+), new vacuum hoses, starter valves synced, beefed up the ground points, series R/R, stator is fine. Did all the checks by the book, everything checks out fine. Only thing I didn't check is vacuum at idle and part throttle, don't have a vacuum meter, but the MAP sensor was reading correct voltage at idle. Didn't check the valves. I circumvented the problem by installing Rapid bike racing and My tuning bike wideband o2 sensor. Extremely expensive and time consuming fix, but it finally consumes the expected amount of fuel, doesn't smell of gas and doesn't spew soot. I did a big ride this weekend, around 700 km, fuel consumption was 6.1 L/100 km (38.5 mpg US) with full luggage and a passenger. Roads were mostly straight, riding 80-130 km/h. Slightly higher fuel consumption was on the highway riding continuously at 130-140 km/h. I've adjusted the target AFR at 5% throttle to be at 13.8 in the cruising range of 4300-6500 RPM, and 14.4 in 10% column to get good fuel consumption. The corrections in 5-10-20% throttle were MASSIVE. Because of that and very rich idle I've adjusted the 0% column to less fuel. The interesting thing is that at high throttle openings 40%+, the corrections are small, which indicates that the flow rate of the injectors is the same as OEM. The massive corrections at 5-10-20 indicate a vacuum leak, but I can't find it. Have to buy a vacuum meter to check. Is it possible that the rubber boots that connect throttle bodies to the cylinder heads have a leak? I never took the throttle bodies off...

[VicSev93]

7 hours ago, gropula said:

I've been battling a similar issue with my '02 VTEC. Always running rich and spewing soot out the exhaust, horrible gas mileage. Almost getting better mileage when riding like a maniac rather civilised riding. I've replaced FPR, sparkplugs, injectors (non-OEM '07+), new vacuum hoses, starter valves synced, beefed up the ground points, series R/R, stator is fine. Did all the checks by the book, everything checks out fine. Only thing I didn't check is vacuum at idle and part throttle, don't have a vacuum meter, but the MAP sensor was reading correct voltage at idle. Didn't check the valves. I circumvented the problem by installing Rapid bike racing and My tuning bike wideband o2 sensor. Extremely expensive and time consuming fix, but it finally consumes the expected amount of fuel, doesn't smell of gas and doesn't spew soot. I did a big ride this weekend, around 700 km, fuel consumption was 6.1 L/100 km (38.5 mpg US) with full luggage and a passenger. Roads were mostly straight, riding 80-130 km/h. Slightly higher fuel consumption was on the highway riding continuously at 130-140 km/h. I've adjusted the target AFR at 5% throttle to be at 13.8 in the cruising range of 4300-6500 RPM, and 14.4 in 10% column to get good fuel consumption. The corrections in 5-10-20% throttle were MASSIVE. Because of that and very rich idle I've adjusted the 0% column to less fuel. The interesting thing is that at high throttle openings 40%+, the corrections are small, which indicates that the flow rate of the injectors is the same as OEM. The massive corrections at 5-10-20 indicate a vacuum leak, but I can't find it. Have to buy a vacuum meter to check. Is it possible that the rubber boots that connect throttle bodies to the cylinder heads have a leak? I never took the throttle bodies off...

 

You know whats interesting, I would think this would never happen to a VTEC due to it having 02 sensors and all that fun emissions stuff. I too, have done everything that you have. Even more, I have taken off the TBs, multiple times to replace all the hoses with OEM, its a good tight fit. I did order a vac gauge. So I will def report back on how it is. But I honestly think everything works as it should. Its just the 98 has no 02, no emissions, nothing. just pretty much straight piped. I would love the rapid racing module. But I think I have to buy that, AND another unit, so they can mimic an 02, or something like that. which is way over 1k in money. Idk if its worth the hassle. 

[DannoXYZ]

Solution may be to get PowerCommander and make adjustments. From gropula's corrections map, it appears factory settings are way, way too rich in low-load cruising zones. Had to remove more than 1/2 of fuel!!! No need for wideband and tuning, he's already done that for you. Just download his map into PC and done! 🙂

[Steampunk]

I'll add my anecdotal two cents.  I have a '98 Gen5 and though it runs well, very smoothly, and when I checked my mileage two weeks ago it was 52MPG.  Because I live at elevation (6600') in Western Colorado and ride anywhere from 5000 to 11000 feet in elevation, the 52MPG is about right.  When I changed the plugs at 22000 miles after purchasing, the old plugs looked a little rich, not overly so though.  Now, to the odor.  It is a stinker at startup.  My last ride I had miscalculated the wind and after starting the bike to put my earplugs in and helmet/gloves on, I was just about gassed out of my garage.  The exhaust tailpiece shows the same slightly rich condition.   

[timmoer]

On 5/4/2023 at 10:12 AM, DannoXYZ said:

Solution may be to get PowerCommander and make adjustments. From gropula's corrections map, it appears factory settings are way, way too rich in low-load cruising zones. Had to remove more than 1/2 of fuel!!! No need for wideband and tuning, he's already done that for you. Just download his map into PC and done! 🙂

Where can I find this? I'd be curious to see what the AFRs are, stock

[DannoXYZ]

On 5/8/2023 at 7:20 PM, timmoer said:

Where can I find this? I'd be curious to see what the AFRs are, stock

Look at PC target-AFR and corrections table above.  At cruising 20% throttle at 5800rpm, he had to reduce fuel by -68% to get 13.8:1 mixture!! Meaning uncorrected factory mapping was way, way too rich!

[timmoer]

13 minutes ago, DannoXYZ said:

Look at PC target-AFR and corrections table above.  At cruising 20% throttle at 5800rpm, he had to reduce fuel by -68% to get 13.8:1 mixture!! Meaning uncorrected factory mapping was way, way too rich!

oh haha - I'm blind! I was wondering what or who gropula is and was trying to google it. Must've been way out of it when I first read your post

[gropula]

Don't take my map as reference, my bike has some unresolved issues. I just said that I have a similar problem and the rapid bike kinda circumvented it by adjusting the fueling by an absurd amount. Also, plugging in this map in PC V is a bad idea, my bike is 6th gen, his is 5th gen. Also, my bike has issues, his has other issues.

[VicSev93]

On 5/2/2023 at 4:06 PM, 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).

 

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 I finally got my vaccume gauge. Attached it to the hose that goes to the MAP sensor. My gauge only has an output of up to 70hg. So the needle went nuts. However, at higher rpms. Like 6k. The needle was pretty steady at 20cmHg. 

 

The gauge only has cm readings and in readings. So idk if that was correct. For this testing purpose.

[VicSev93]

On 5/1/2023 at 7:21 PM, VicSev93 said:

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. 

 

OK! Hello all. I am bringing back this thread because I think I found my issue. But I need help in further diagnosis. So I plugged up my vaccume gauge that just came in not too long ago. Pulled the hose from the MAP into the gauge. I could NOT get a food reading. The arrow was way too sporadic. I will attach a video. 

 

My gauge came with a handy instruction booklet. That states if the needle is sporadic and with the ride of RPMs becomes more stable. The issue is either. 

 

1) ignition and or timing. 

 

2) carb mixture adjustment at idle. (In my case the TB sync. 

 

Any idea how to check if my ignition is on point? 

 

Thank you

[DannoXYZ]

When was last time valve-clearances and cam-timing was inspected?

[VicSev93]

9 hours ago, DannoXYZ said:

When was last time valve-clearances and cam-timing was inspected?

I would say about 4k miles ago. Everything was in spec. I can always recheck ofc.