Possible Injector issue?

[bryanhes]

I have a low RPM issue on my 2003. It hesitates and sputters a bit up until about 3k. If you roll on the throttle fairly decent and get above 4k it smooths out. I'm thinking it is injector related from sitting too much.  I haven't run any injector cleaner through it yet but thought I would get some opinions on either a reputable injector cleaning company or buy a new set. Or any injector cleaners recommended on the Birds? It is afterall 23 years old but less than 11,000 miles on the clock. 

 

I appreciate the feedback!

Edited September 15 by bryanhes

[SwampNut]

I had to clean three of them on my "new" XX because it had sat for 5-10 years.  It's not hard to do.  Is taking them out yourself something you feel confident in?

 

[bryanhes]

1 hour ago, SwampNut said:

I had to clean three of them on my "new" XX because it had sat for 5-10 years.  It's not hard to do.  Is taking them out yourself something you feel confident in?

 

No problem wrenching. I do pretty much all mechanic work. Haven't removed any of these though. What did you clean them with? Thought about running an additive through since it was started regularly but not ridden much over the last 3 years or so but I think additives only do so much. 

[poida]

ive put a bottle of injector cleaner in my 99 bird after it sat for too long.it spluttered for a while but eventually sorted itself out

[Zero Knievel]

2 hours ago, poida said:

ive put a bottle of injector cleaner in my 99 bird after it sat for too long.it spluttered for a while but eventually sorted itself out

Yes.  A tank or three of gas with a high quality injector cleaner would save a lot of work.

[tomek]

KISS. keep it simple stupid.😁

Check vacuum lines, or best replace them piece by piece. Much easier vs. removing them all at once and then later trying to figure out what goes where.

 Get couple feet of bulk lines, etc.

And voltage with bike running.

[bryanhes]

2 hours ago, tomek said:

KISS. keep it simple stupid.😁

Check vacuum lines, or best replace them piece by piece. Much easier vs. removing them all at once and then later trying to figure out what goes where.

 Get couple feet of bulk lines, etc.

And voltage with bike running.

Not a bad idea to check due to age but since the sputtering is only happening at low RPM, I tend to think its fuel delivery issue. If vacuum hoses were compromised my experience is typically a lean fuel mixture across the RPM range not just low range. Get past the 3500- 4000 she rips.

Edited September 15 by bryanhes

[SwampNut]

13 hours ago, bryanhes said:

No problem wrenching. I do pretty much all mechanic work. Haven't removed any of these though.

 

Then you got this, no problem.  It's easy but takes a lot of time.  It will become super obvious as you get into it.  I agree that running a concentrated amount of FI cleaner in the tank is a good first try.  In my case, three were so clogged that they wouldn't even fire at all, zero flow, and the input had a gel version of fuel in them.  So no contact with gas/cleaner.

 

Here's the basics, tell me if your FI cleaner doesn't do it and I can write up more.  The injectors can fire just with 9-12v from any power supply or a battery.  So you can put it in a vise or clamp, put a little cleaner in it, and then cycle it with power.  This will flow the cleaner, then you can let it soak, repeat.  In my case since they were so awful, I put them into a bath of 50/50 gas and FI cleaner, in a bag, and then put that in our ultrasonic cleaner for 15 minutes.  They are fully good as new.  I got new o-rings for them at the Acura dealer, since Honda shares parts between cars and bikes.

 

Overall, not rocket surgery just hours of work.

[tomek]

1 hour ago, bryanhes said:

Not a bad idea to check due to age but since the sputtering is only happening at low RPM, I tend to think its fuel delivery issue. If vacuum hoses were compromised my experience is typically a lean fuel mixture across the RPM range not just low range. Get past the 3500- 4000 she rips.

 You think it is lean or rich type of sputtering below 3500-4000 rpm? 

 IIRC XX has a reference type of fuel pressure regulator, so vacuum hose leak would cause rich running at anything below full throttle, and relatively poor milage. But honestly, it would not cause misfire, just poor mpg. 

 

 But I would check voltage across rpm range/load for sure. 

[ironmike]

A couple of thoughts . . . Two other potential issues, one of which has already been mentioned--the FPR. A compromised internal diaphragm (even a pinhole) can contribute to erratic fueling and will only further deteriorate until mileage noticeably suffers. Fortunately, the fix--replacing the FPR--is relatively easy.

The other issue, while somewhat rare is very often overlooked--compromised integrity of spark plug wiring. To be precise, it's not really traditional wire (hasn't been for decades, since the advent of electronic ignitions); it's carbon impregnated cloth (think thin rope/twine) covered in layers of rubberized insulation that can deteriorate with age, repeated ambient heat cycling, and exposure to a host of chemicals and environmental factors. Cracks developed in the surface of such insulation are not always easily visible but become increasingly susceptible to moisture, fluctuating resistance, and potential ground arcs at various rpms (missing/sputtering). Until you can see actual arcing under reduced lighting conditions, it's typically hard to diagnose.

Now combine a misbehaving FPR with deteriorating plug wiring and you've got a pair of frustrating gremlins sneering at you while they hide behind each others' manifest symptoms--sneaky bastards!  

[fizzy]

One more thing to check: if the FPR (fuel pressure regulator) has a pinhole leak, which is common, it will send excess raw fuel to 1 cylinder only, causing poor running which will clear up at high rpm/throttle opening.

 

Check is.... after a run, pull vacuum hose off FPR (mushroom shaped device RHS fuel rail) and check for fuel in the hose. if ok It will be DRY DRY DRY. 

[bryanhes]

3 hours ago, SwampNut said:

 

Then you got this, no problem.  It's easy but takes a lot of time.  It will become super obvious as you get into it.  I agree that running a concentrated amount of FI cleaner in the tank is a good first try.  In my case, three were so clogged that they wouldn't even fire at all, zero flow, and the input had a gel version of fuel in them.  So no contact with gas/cleaner.

 

Here's the basics, tell me if your FI cleaner doesn't do it and I can write up more.  The injectors can fire just with 9-12v from any power supply or a battery.  So you can put it in a vise or clamp, put a little cleaner in it, and then cycle it with power.  This will flow the cleaner, then you can let it soak, repeat.  In my case since they were so awful, I put them into a bath of 50/50 gas and FI cleaner, in a bag, and then put that in our ultrasonic cleaner for 15 minutes.  They are fully good as new.  I got new o-rings for them at the Acura dealer, since Honda shares parts between cars and bikes.

 

Overall, not rocket surgery just hours of work.

Thanks for the info SwampNut! I think I recall you mentioning this one sat for a number of years. Any particular FI cleaner you have had success with?

[bryanhes]

2 minutes ago, fizzy said:

One more thing to check: if the FPR (fuel pressure regulator) has a pinhole leak, which is common, it will send excess raw fuel to 1 cylinder only, causing poor running which will clear up at high rpm/throttle opening.

 

Check is.... after a run, pull vacuum hose off FPR (mushroom shaped device RHS fuel rail) and check for fuel in the hose. if ok It will be DRY DRY DRY. 

Thanks fizzy, I'll take a look at the FPR as well. Getting ready to do a complete fluid change on the bike to include brake fluid, coolant (likely a thermostat) and oil so I will be pulling the fairings.

[bryanhes]

3 hours ago, tomek said:

 You think it is lean or rich type of sputtering below 3500-4000 rpm? 

 IIRC XX has a reference type of fuel pressure regulator, so vacuum hose leak would cause rich running at anything below full throttle, and relatively poor milage. But honestly, it would not cause misfire, just poor mpg. 

 

 But I would check voltage across rpm range/load for sure. 

I just meant that I was thinking if it was a vacuum hose leak it would likely cause it to run lean across the rpm range and not just the lower side. Maybe I am wrong in my thinking? I also have a little learning to do on the Bird's FI system and components. I'll give all of that a good looking over this weekend once I pull the fairings and put it on the lift. I appreciate the info!

[SwampNut]

33 minutes ago, bryanhes said:

Any particular FI cleaner you have had success with?

 

I don't think it matters in super concentrations like what I used, and at lower ones, not sure.  I believe that @superhawk996 recommended Techron once.

 

31 minutes ago, bryanhes said:

Thanks fizzy, I'll take a look at the FPR as well.

 

NOTHING should come out of it when running.  Anything dumped goes to the first cylinder as he said.  Mine was flowing like crazy.

[superhawk996]

A leaking FPR will have a bigger effect at low RPM and low load than higher so it's definitely something to check.  If it's good then try injector cleaner, Techron is my go-to, but anything with PEA 'should' be good.

[superhawk996]

PEA= polyetheramine.  

[SwampNut]

11 minutes ago, superhawk996 said:

PEA= polyetheramine.  

 

Ooooooohhh.

 

[SwampNut]

Injector ring info:

 

7.3 x 2.2

 

91301-P2F-A01

 

16074-ZY3-000

 

 

 

This O-ring fits numerous Honda models including:

 

 

• Honda Accord (2-door coupe, 4-door sedan, 5-door hatchback, wagon, Aerodeck models from 1994-1997)
• Honda Civic (coupe, hatchback, sedan, Aerodeck)
• Honda CR-V
• Honda CRX Del Sol
• Honda HR-V
• Honda Integra
• Honda Legend
• Honda Logo
• Honda NSX
• Honda Prelude
• Honda S2000
• Honda Shuttle

[bryanhes]

On 9/15/2026 at 2:54 PM, SwampNut said:

 

I don't think it matters in super concentrations like what I used, and at lower ones, not sure.  I believe that @superhawk996 recommended Techron once.

 

 

NOTHING should come out of it when running.  Anything dumped goes to the first cylinder as he said.  Mine was flowing like crazy.

Added some Techron to the tanks yesterday and took it for about a 40- 50 mile ride, still sputtering under 4k. I'm going to pull the fairings this weekend to check the FPR. Do you mean to pull the vacuum hose while running and not after shutting it off?

[fizzy]

No need to pull fairings. Remove seat then 2 tank bolts and rotate tank up 6" and support somehow....best if tank is on E.  Watch out for 2 tabs that attach to tank from infill panels   Reach in and pull vac line off of the FPR with engine recently turned off.  As stated, line must be dry. 

 

[bryanhes]

1 hour ago, fizzy said:

No need to pull fairings. Remove seat then 2 tank bolts and rotate tank up 6" and support somehow....best if tank is on E.  Watch out for 2 tabs that attach to tank from infill panels   Reach in and pull vac line off of the FPR with engine recently turned off.  As stated, line must be dry. 

 

Thanks Fizzy, I had watched a video where they removed the fairings to replace the FPR and assumed it needed to be done. Maybe if I need to replace it? I have thought about just ordering this kit from Quantum and replacing everything as preventative but always had the mindset of "If its not brokeen". On the other hand it is still a 23 year old motorcycle. Anyone used Quantum for parts if the FPR is needed? They sell it alone as well. https://www.highflowfuel.com/fuel-pump-w-fuel-pressure-regulator-tank-seal-fuel-filter-strainer-for-honda-motorcycle-oem-replacement-hfp-382-yt30rf-qfs/

[fizzy]

Before you start to replace parts willy nilly, I would recommend to nail down the running issue first. But yes, the parts you show above would be good preventative maintenance. 

 

FYI: in the event to remove the fuel rail, remove the tank, not just lift it. Best bet is to siphon all the fuel out first. Fairings can stay in place. 

[bryanhes]

3 hours ago, fizzy said:

Before you start to replace parts willy nilly, I would recommend to nail down the running issue first. But yes, the parts you show above would be good preventative maintenance. 

 

FYI: in the event to remove the fuel rail, remove the tank, not just lift it. Best bet is to siphon all the fuel out first. Fairings can stay in place. 

I'm not replacing it unless there is a sign of leakage, that doesn't make sense to me either. I was asking if anyone had used Quantum if it needs the FPR. 

[SwampNut]

16 hours ago, fizzy said:

No need to pull fairings. Remove seat then 2 tank bolts and rotate tank up 6" and support somehow....best if tank is on E.  Watch out for 2 tabs that attach to tank from infill panels   Reach in and pull vac line off of the FPR with engine recently turned off.  As stated, line must be dry. 

 

 

Yeah this, and a piece of 2x4 or 4x4 will help hold the tank area open.  I've done this a lot.  I got my FPR from Partzilla, at the time it was the last one in the country.  There are third party versions on eBay.  I made a bunch of calls and it really was the only one in the country.  I was surprised to see how every dealer now has access to every other dealer's inventory.  Hopefully they've restocked?

 

I had to look, back in stock:  https://www.partzilla.com/product/honda/16740-MAT-E22?ref=7cc2d06c61c94b967b14df385071e26be34292df