Very noticeable flat-spot/sputtering in power-band between 4-4.5krpm

[Polishblood]

Hello,

When I bought my 2008 xb9sx (6+ months ago), I noticed a flat-spot in power-band around 4-4.5krpm. It's been getting worse and more noticeable ever since.

It happens when I am using normal throttle operation, 50% roll on, to WOT operation, 100% roll on. (With the WOT roll on, the flat-spot can occur for a duration of up to 2 full seconds. Like literally my friends will be accelerating and my bike feels like it is just coasting with no power). As soon as the flat-spot/sputter is gone, by bike instantly kicks back into life with tons of torque. So top end power is very good. Literally the problem occurs only between 4-4.5krpm.

(Under 3 conditions is the symptom less noticeable/avoidable) #1 To avoid the flat-spot or sputter, I have be VERY smooth on the throttle, roll on super slowly, and it won't happen. #2 If the fuel tank is topped off, especially with fresh gas, it is less noticeable. #3 When rolling on (normal to WOT) in first gear, sometimes the symptom is non-existent. The bike seems to power through it due to gearing.

Bike has 12k miles. No check engine lights or codes (I think). Air-Filter was cleaned recently. Did a TPS reset, might do another. Spark plugs are new and gapped (I am using the colder ones). Stock exhaust. Everything is pretty much stock but air filter which is K&N.

Do our xb9 bulls have two sets of injectors? Perhaps a second set of injectors that come on around 4-4.5krpm? Perhaps they are dirty? Bad fuel pressure? Although as I mentioned before, top end power is very good. So is low end power. Maybe bad AMPS to fuel pump?

Would like to heard your thoughts. Thank you!

 

[JeffY]

Mine only has one set of injector (03), I would say check fuel pressure I think it should be around 50 psi, and have you checked your timing?

 

[Peeking Turtle]

You figure anything out with this one? I've been waiting for some of the gurus to chime in.

 

[Triumph1050]

Had an 07 xb12Stt and I had something similar happen to me however my check engine would come on along with the issue. It would be right around 4000 - 4500 rpm's it would sputter and ride like hell, got worse and worse. I tried TPS reset and all of that but I eventually figured out that I needed to just clean off my ground cables as they were corroded from the salty air (So Cal by the beach). My battery was overdue for a change too but it literally was just the ground connection, so maybe check your ground wires that are mounted to the subframe.

 

[Malaguita]

Have you checked "Noise reduction" on your ECM?
Sounds like "White Wire Mod".
In Ecmdroid: Ecm Parameters, General Config, Noise reduction.... Only Ramp Out enabled.

 

[Cooter]

Do you have access and ability to use diagnostic tools like ECMDroid?

You can check for historical codes, and go to "Live Data" and check the TPS, CPS.... and about a million other items to diagnose it.

Otherwise we're guessing....

 

[njloco]

Guy's, your slipping, this is from JUNE !

 

[Cooter]

I saw that NJ, just correcting some odd info:angel:

 

[Polishblood]

Hello friends. Two years later and I am still dealing with the same issue. Now that the coronavirus is giving me more time at home, I want to fix this issue immediately.

I need your diagnostic help. Everything that I said in the original post applies. To clarify, it is not a complete loss of power or even a sputtering issue, rather its a large hesitation in power which is happening at EXACTLY 4,500rpms. The bike runs AMAZING at every other rpm.

My thoughts are that it maybe an oxygen sensor, IAT, fuel injector, or fuel pressure related issue. What are your thoughts? Could these items be the issue? How do I go about diagnosing these items? I am unfamiliar with the diagnostic software out there so please leave a link if you mention one.

Let's get this done guys. I am looking forward to everyone's expertise.

Cooter, you mentioned ECMDroid, I will look into it tonight.
Triumph, ground cables are good and attached well.
Malaguita, never heard of the "white wire Mod". What is it? I will try to check it out tonight.

 

[34nineteen]

Your first step would be to get a service manual. Being that you asked if the motorcycle has 2 sets of injectors per cylinder tells a lot.

And yes, it does sound like the 2nd set isn't kicking in and the sensor probably needs to be recalibrated using dedicated service equipment. There are actually 4 sets of injectors per cylinder. The first set does idle to 1500 rpm, the second covers 1500-3000, the third covers 3000-4500 and the 4th set covers 4500-redline. On the 1125's all the injectors kick on at once, which is why they make so much more power than an XB.


For someone who wants to fix an issue "immediately", you're are going to wait until "tonight" to look into diagnostic tools? Is Bridgewater in Hawaii?


Start your diagnosis here... www.buelltooth.com. Tell him Cooter sent you, not me...

 

[Polishblood]

Your first step would be to get a service manual. Being that you asked if the motorcycle has 2 sets of injectors per cylinder tells a lot.

And yes, it does sound like the 2nd set isn't kicking in and the sensor probably needs to be recalibrated using dedicated service equipment. There are actually 4 sets of injectors per cylinder. The first set does idle to 1500 rpm, the second covers 1500-3000, the third covers 3000-4500 and the 4th set covers 4500-redline. On the 1125's all the injectors kick on at once, which is why they make so much more power than an XB.

For someone who wants to fix an issue "immediately", you're are going to wait until "tonight" to look into diagnostic tools? Is Bridgewater in Hawaii?

Start your diagnosis here... www.buelltooth.com. Tell him Cooter sent you, not me...

check once more for historical fault codes. if you find one or more in the "50 series" it's a failing ECM. before replacing check the dedicated ECM ground wire for integrity and continuity.
otherwise...classic failing fuel pump. service it.

Thank you for the detailed information gentlemen. I just ordered the BUELLtooth ECM Interface off of www.buelltooth.com. I look forward to using it and hopefully it comes in sooner than later. I will keep you guys updated with any information/questions I may have.

Lunaticfringe, with regards to Buells, does a classic failing fuel pump exhibit a dip in power at 4,500 rpm?

 

[Cooter]

In stock form these have a slight dip in mid-range power you can see on a dyno chart. Its not as extreme as you describe though.
Yes. High load/high RPM put a strain on a fuel pump and will expose a weak one. Easy swap, and Lunatic has the stuff if you need it.

IMO, I wouldn't start guessing quite yet. Wait for the diagnostic device to show up and use it to narrow down the causes. Unless you like frustration, expense, and added time? Lol, keep us posted.

 

[Polishblood]

I read in the electronic diagnostics manual that an oxygen sensor reading below <0.41 indicates a lean mixture and a reading of >0.56 indicates a rich mixture. I have no clue if I am using ECMdroid correctly however I had my bike idling and the O2 sensor reading was fluctuating between 0.1-0.7. Therefore I couldn't accurately tell where the average reading was. ALSO forgot to mention that my exhaust does smell like gas which correlates to a rich mixture (AFV of 0.82%). However last time I checked my spark plugs, they were white with a hint of browning (they did not look flooded at all). So I am baffled. I will check my plugs again.

Using ECMdroid I performed a front and rear injector test. When performing the front injector test, I heard 5 sequential taps. (tap tap...tap tap...tap). When performing the rear injector test, I heard 5 taps in the same manner as the front.

Questions:

Is there a list of what all data variables in ECMdroid mean/are testing? Also is there a normal value list for the variables? For example, I don't know the difference between "02" and "021"... or if "inj1 ADC" is suppose to read 0 while the bike is running.

Are there any tests in ECMdroid that you guys recommend I do?

How can I further check my injectors? Perhaps only the 4th set of injectors are not working properly, therefore tripping the low AFV (rich mixture) and not showing any symptoms of flooding at the plugs. I don't know. Kind of baffled.

 

[Cooter]

What is the problem you are trying to find?

 

[Jonus]

So I went for a ride today and my bike started doing this exact thing at the same rpm. This is just theory but isn't this the point at about 4.5 rpm under 50 to 75% throttle the mapping exits out closed loop learn to open loop? If the mapping was heavily altered in the closed loop learn would that difference transitioning to open loop cause the blip? Anywho, I reflashed the stock race map to see if that was it. Won't know till I take it out for another ride.

 

[Polishblood]

So I went for a ride today and my bike started doing this exact thing at the same rpm. This is just theory but isn't this the point at about 4.5 rpm under 50 to 75% throttle the mapping exits out closed loop learn to open loop? If the mapping was heavily altered in the closed loop learn would that difference transitioning to open loop cause the blip? Anywho, I reflashed the stock race map to see if that was it. Won't know till I take it out for another ride.

Yea, my theory as well. During closed loop, the oxygen sensor is compensating for a problem. Since the AFV is significantly different between closed and open loop, I am noticing a blip or hesitation in power.

My AFV was 82%. So the oxygen sensor is sensing a rich condition in the exhaust and is compensating for it by adding less fuel. So what's causing the rich condition? I don't know however I just checked my spark plugs. Front spark plug looks light tan all around. Rear spark plug looks 50% brown and 50% white/barely tan. So front looks slightly lean but ok and rear looks like it's experiencing both a lean and rich? (will post pictures of plugs soon). The rear plug correlates to the oxygen sensor since the oxygen sensor is located on the rear exhaust.

If I saw that my plugs, especially the rear one, were bone white (indicating an obvious lean mixture) and my oxygen sensor was reading rich, I would definitively diagnose my problem as having a faulty oxygen sensor. That is not my case however I am not excluding my oxygen sensor just yet.

I switched the plugs again, this time from the NGK DCPR9EIX, which EVERYONE recommends, to the OEM spark plugs which are called 10R12X (part number 27794-08). These OEM spark plugs are advertised foul resistance. I felt a difference. From 0-3krpm, the bike seems less powerful (in fact I almost stalled twice the first ride) however acceleration feels smoother throughout the entire rpm range (less cammy). Also, the 4.5krpm hesitation happens ALOT less. It use to happen 80-90% of the time when hitting 4-4.5krpm, now it happens only 5-15% of the time.

I checked my AFV with buelltooth after switching the plugs back to the OEM. AFV was 82% and now it is 90%. I still don't think I fixed the problem. I ride at an altitude of only 150 feet above sea level. I believe my AFV should be above 100% or at least near 100%. i will write up another post below explaining what I think the problem might be.

 

[Polishblood]

Left spark plug in both pictures is the front spark plug. Right spark plug in both pictures is the rear spark plug.

 

[Cooter]

Plugs look good. How does it run when you re-set the AFV to 100?

Still just totally guessing... but you could have an old/fouled/lazy O2 sensor.

and I never recommend this, but you could save your existing .xpr file with ECMDroid and try a new stock program. I don't know any history of your bike, so I don't know if it's a stock program or if you have been messing with it, but an overly rich condition that the ECM is trying to correct is common with all that.

 

[Polishblood]

So as mentioned before, I installed the OEM spark plugs and the bike's main symptom, hesitation between 4-4.5krpm, was significantly reduced. Occurrence dropped from 80-90% to 5-15% of the time. AFV is now 90% vs 82%.

I normally road the bike on and off for the past 2 years. After recently riding the bike for about 200 miles I noticed a couple more symptoms. None of these symptoms are new but I never paid attention to them because they were not noticeable. After installing the OEM spark plugs, which seemed to make the bike accelerate more smoothly, some of these symptoms became more noticeable. I will list everything below.

List of all symptoms (revised after installing OEM plugs)

1. 4-4.5krpm hesitation occurs less when riding briskly (exact opposite with old spark plugs). Hesitation does not occur when the bike is cold.
2. Strong smell of gas when parked after ride
3. Very slight bucking at various rpm between 2k-4.5krpm (closed loop).
4. Idle sways between 1-1.2krpm after cold start, levels out after 10 seconds (is this normal?)

Possible Problems

1. Faulty oxygen sensor (however plugs show overall good burn)
2. Faulty Fuel Injectors or O-rings leaking

I ordered both an OEM oxygen sensor and fuel injectors w/ intake seals. I already did the service manual fuel injector test (ignition on and off 5 times to build fuel pressure). The fuel injectors are dry. I have a feeling the leaking only starts when the bike is warm. I can test that out. Checking the injectors with a mirror after coming back from a ride.

Questions:

Do I need to remove the throttle body to replace the fuel injectors? Any advice on replacing the injectors?

 

[Polishblood]

I have yet to set the AFV to 100. How long will the AFV stay at 100 if I don't disable closed loop? I'm shying away from saying it is the oxygen sensor because it appears to be doing its job. Plugs look relatively good.

I think it maybe the fuel injectors or o-rings around them that are leaking at higher temperatures.