Jump to content

Awful Engine Noise and Bike Won't Pull (at speed)


Recommended Posts

  • Supporting Member

I am chasing a nasty gremlin. When in A-mode (flashed, quick turn), something really odd is happening when I get to 7,000 RPM. The engine sounds like what I can best describe as a rattling can of nails, the RPM gauge remains at ~7,000 RPM, and the engine stops pulling/accelerating... but doesn't die or sputter. I don't detect any jarring, clutch slipping etc.... just loss of acceleration and the awful sound. All returns to normal when I ease up on the throttle. This does not happen in any other mode. I can comfortably and predictably take the bike to the red line in STD and B modes. The bike otherwise starts and runs very well and I continue to ride the thing.

Detected this issue at the end of last season, and thought it might have been an issue with the quick-turn map, but I am told that this can not be the case. Suggestion was that TPS might be defective, but I am having a hard time understanding how it would affect the bike in only one mode.

While I am waiting for my re-flashed ECU to return from Vcyclenut (not related to this issue), I tested both outputs of each sensor (there are two in each), individually and in parallel. All values check out and are within spec. Sensors remained on the bike.

I also checked for values across the sweep for each sensor output. Of the two sensors, APS readings for each output were gradual and consistent as I moved the throttle from closed to open and back, using both slow and quick action. No issues with APS that I could discern.

When exercising the TPS (moving the throttle plates from closed to open and back), one of the outputs wasn't consistent, i.e. the meter would show open circuit for a fraction of a second in various positions (mostly toward 50% open). It was difficult to capture because of the very brief instant when this occurred... and because moving the plates was more step-like than linear.

Anyway... thought I'd share and see if anyone has ever come across this. The only electrical mod that I can think of that integrated with these circuits was MCCruise (APS), but this issue did not exist until late last season. I will disable CC and see what happens.

Edited by piotrek

canada.gif.22c5f8bdb95643b878d06c336f5fe29f.gif

Link to comment
Share on other sites

  • Supporting Member

That’s a new & unique one, @piotrek.   The noise you describe sounds mechanical (typically a Very Bad Thing), but the behavior certainly sounds more electrical.  Wish I had more to offer, but it sounds like you’re doing the right things to try and troubleshoot.  

Good luck!   I can’t wait to hear what you find.  

  • Thumbsup 1
Link to comment
Share on other sites

If you can go through the gears up to 10,000 rpms in STD and B mode 2nd through 6th gear and everything is OK, pulls hard, no noises but in A mode it does as you describe it defiantly sounds like an electrical problem. In A mode does it do this in 2nd or 3rd or 5th gears, only 6th? All gears? It doesn't sound like an electrical connection or it would happen no matter what mode, in other words re-plugging all connections probably won't make a difference. Hopefully the re-flash will give you some answers.

  • Thumbsup 1

Ain't no fun when the rabbit gets the gun!

Link to comment
Share on other sites

  • Supporting Member
2 hours ago, phpaul said:

Any chance it's ignition knock from too much advance?  I don't know but I'm wondering if the ignition advance curve is mapped separately for each mode.

Yes, they change fueling and some ignition parameters but they do this repeatedly on a dyno up to WOT. and the flash is built for everyone.  Something makes me think APS or TPS, the A-mode settings are 'quick-turn' throttle and the throttle 'travel' is different than STD or B mode.  Am I way off in my thinking?🤷‍♀️

  • Thumbsup 1

***2015 Candy Red FJ-09***

Link to comment
Share on other sites

56 minutes ago, betoney said:

Yes, they change fueling and some ignition parameters but they do this repeatedly on a dyno up to WOT. and the flash is built for everyone.  Something makes me think APS or TPS, the A-mode settings are 'quick-turn' throttle and the throttle 'travel' is different than STD or B mode.  Am I way off in my thinking?🤷‍♀️

Not at all.. in fact the biggest difference between the A, B, and STD modes is how fast the throttle plates move in response to your wrist. I have seen this on the dyno as well: when you put a load on the bike and go WOT very rapidly with your wrist in 3rd or 4th gear (usually), the corresponding value that the various software interprets (flashtune, PC-V, Winpep7,8, etc) show a delay in reacting.

Difficult for me to explain by typing, but you can watch the value on the screen for Throttle Percentage NOT keep up with your wrist movement. This is the delay built into each map at various throttle positions: the ECM fires the stepper motor of the YCC-T system at different speeds depending on mode selection (and I'll bet lots of other variables that we riders aren't aware of...)

-Skip

  • Thumbsup 1
Link to comment
Share on other sites

4 hours ago, tktplz said:

If you can go through the gears up to 10,000 rpms in STD and B mode 2nd through 6th gear and everything is OK, pulls hard, no noises but in A mode it does as you describe it defiantly sounds like an electrical problem. In A mode does it do this in 2nd or 3rd or 5th gears, only 6th? All gears? It doesn't sound like an electrical connection or it would happen no matter what mode, in other words re-plugging all connections probably won't make a difference. Hopefully the re-flash will give you some answers.

@piotrek I'd love to know the answers to some of these questions too... it's sounds as if you can duplicate the symptom fairly regularly...

-S

  • Thumbsup 1
Link to comment
Share on other sites

  • Supporting Member

Thank you all for chiming in with ideas. I will continue to simmer in these, and once I have my ECU back I will get right on with the task of narrowing the issue. Engine knocking did cross my mind, and APS/TPS remain in the crosshairs. Will try different fuel octane and tweak my APS... etc. etc.. I sent the ECU for a re-flash (for the exhaust) in February and mentioned this to Dave. He was doubtful that the re-flash would fix the issue... and he was right.

I have experienced this in gears 2 through 5... that's not to say it's not there in the others, but I just haven't been there. The bike works great otherwise... starts great, fuel consumption is OK, pulls hard, doesn't burn oil, plugs are clean etc. I suspect this to be fuelling/ignition related. @betoney... the quick-turn, or 3/4-turn was explained to me as ramping up to full throttle in 3/4 of a regular full twist. I do suspect it has something to do with the issue... and maybe repositioning the APS could fix this.

TBC

 

  • Thumbsup 2

canada.gif.22c5f8bdb95643b878d06c336f5fe29f.gif

Link to comment
Share on other sites

  • Supporting Member
11 minutes ago, skipperT said:

@piotrek I'd love to know the answers to some of these questions too... it's sounds as if you can duplicate the symptom fairly regularly...

-S

I will get methodical with this once I have my ECU back... but the one constant appears to be ~7,000 RPM. It's either that or a particular throttle (grip and/or plate) position. More questions than answers at the moment.

  • Thumbsup 1

canada.gif.22c5f8bdb95643b878d06c336f5fe29f.gif

Link to comment
Share on other sites

17 hours ago, piotrek said:

I am chasing a nasty gremlin. When in A-mode (flashed, quick turn), something really odd is happening when I get to 7,000 RPM. The engine sounds like what I can best describe as a rattling can of nails, the RPM gauge remains at ~7,000 RPM, and the engine stops pulling/accelerating... but doesn't die or sputter. I don't detect any jarring, clutch slipping etc.... just loss of acceleration and the awful sound. All returns to normal when I ease up on the throttle. This does not happen in any other mode. I can comfortably and predictably take the bike to the red line in STD and B modes. The bike otherwise starts and runs very well and I continue to ride the thing.

Detected this issue at the end of last season, and thought it might have been an issue with the quick-turn map, but I am told that this can not be the case. Suggestion was that TPS might be defective, but I am having a hard time understanding how it would affect the bike in only one mode.

While I am waiting for my re-flashed ECU to return from Vcyclenut (not related to this issue), I tested both outputs of each sensor (there are two in each), individually and in parallel. All values check out and are within spec. Sensors remained on the bike.

I also checked for values across the sweep for each sensor output. Of the two sensors, APS readings for each output were gradual and consistent as I moved the throttle from closed to open and back, using both slow and quick action. No issues with APS that I could discern.

When exercising the TPS (moving the throttle plates from closed to open and back), one of the outputs wasn't consistent, i.e. the meter would show open circuit for a fraction of a second in various positions (mostly toward 50% open). It was difficult to capture because of the very brief instant when this occurred... and because moving the plates was more step-like than linear.

Anyway... thought I'd share and see if anyone has ever come across this. The only electrical mod that I can think of that integrated with these circuits was MCCruise (APS), but this issue did not exist until late last season. I will disable CC and see what happens.

Great info here, sounds like you've dived in quite thoroughly.  I have a couple questions:

When you state that "i.e. the meter would show open circuit for a fraction of a second in various positions (mostly toward 50% open)" what roughly were the resistance values and/or do you think that it could have happened right at the same time that your VOM "autoranged" from ohms to k-ohms (for example)?

This is a very important bit of data: I've checked TPS wiper mechanisms many times and want to make sure that what you are seeing is indeed a bad spot in the wiper mechanism as opposed to the meter switching ranges. Other people have been fooled by their meter into thinking that the TPS had a bad spot when this occurs when in fact the VOM was simply blinking OL briefly while it switched ranges.  Another way to check the TPS is by backprobing the connectors and watching the voltage changes while it is operating. This may not be possible however if the ECM restricts movement of the throttle plates due to the engine not actually running while it's being tested. However on 15-16 models you can operate them in ALL positions in DIAG mode. BE SURE that your battery is hooked up to a tender while performing these tests live, as a weak battery will also skew your results.

Other thoughts:

-based on your testing being sound and accurate, a new TPS might definitely be a good part to replace.

-However a bad TPS being the cause of your issue doesn't make why this issue only happens in A mode. The only reason I can think of would be because the ECM is asking the YCC-T system to operate at a higher rate of speed and that's why the bike is only symptomatic in A mode.

-Even though V-cyclenut claims this can't possibly be a flash issue I'm not 100% convinced of that fact and think that it's a good idea that you are getting your ECM reflashed again.  The only way to know for sure would be to install your ECM Into a buddy's bike and see if his bike suddenly develops the problem in A mode.

-Spark plugs: what type are you running and when were they last replaced? I ask because @phpaul may be on to something. The FJ/MT doesn't have a knock sensor like a car such that the ECM will pull ignition timing when it detects combustion knock. However in A- mode the timing might be advanced enough that it could place a higher demand on your ignition system and it just so happens that you might be loosing spark which would cause a rough running condition if you were to "loose a cylinder" while accelerating hard in A-mode. I'd recommend you replace your spark plugs just as a troubleshooting step to rule them out as the cause of your problem.

-Any stored DTC's?

***

Hopefully some of this info helps, keep us posted.

-Skip

  • Thumbsup 2
Link to comment
Share on other sites

So my GSXR had a problem similar. It wouldn't rev above 7,000 RPM or such, and it ended up being the stator/CPS. However, I don't think it's the issue here because your bike works in B & STD mode, possibly worth discussing though.

Good luck!

  • Thumbsup 1

'15 FJ09

Link to comment
Share on other sites

  • Supporting Member
7 hours ago, skipperT said:

When you state that "i.e. the meter would show open circuit for a fraction of a second in various positions (mostly toward 50% open)" what roughly were the resistance values and/or do you think that it could have happened right at the same time that your VOM "autoranged" from ohms to k-ohms (for example)?

I was able to conduct this test more slowly, and can repeat the condition on the one suspected pot. The meter doesn't show open, but resistance dips in consistently the same spot, and as measured in both directions of the sweep. It dips to 0.17K somewhere around 1.8K. Throttle plate positions are different depending on which direction of the sweep is being measured. Not even sure any of this is an issue, but it is what I am seeing. This is still all present in STD and B modes.

20200427_174350.thumb.jpg.37e0e60c4e751aa22bbe81634d4097d9.jpg20200427_174336.thumb.jpg.76c92ce33c522b7912b54518ddd8c08f.jpg

Have some measurements to share, but these are fixed minimum and maximum values and don't quite tell the story, but for reference...

Capture1.thumb.PNG.ffeeadeef79a93a8a8979eba4c553a60.PNG

7 hours ago, skipperT said:

Even though V-cyclenut claims this can't possibly be a flash issue I'm not 100% convinced of that fact and think that it's a good idea that you are getting your ECM reflashed again.

The ECU was already re-flashed and the condition did not go away... appears unique to my bike. You'd think it would have come up on another machine at some point if the flash were bad. I could not find anything resembling what I am experiencing.

7 hours ago, skipperT said:

Spark plugs: what type are you running and when were they last replaced?

Plugs are fresh... Iridium CR9EIA-9. Have been running these for 4 years now. 91-94 octane fuel as available.

7 hours ago, skipperT said:

Any stored DTC's?

ECU did not throw any codes that I could see... but I have not checked for any stored codes. Will have to force the condition and take it from there.

Edited by piotrek
  • Thumbsup 1

canada.gif.22c5f8bdb95643b878d06c336f5fe29f.gif

Link to comment
Share on other sites

  • Supporting Member
6 hours ago, koth442 said:

So my GSXR had a problem similar. It wouldn't rev above 7,000 RPM or such, and it ended up being the stator/CPS.

Interesting. I came across an issue on the R1 forum, engine making a rattling-like racket at higher RPM. That was due to a bad EXUP valve... which we don't have on this bike.

canada.gif.22c5f8bdb95643b878d06c336f5fe29f.gif

Link to comment
Share on other sites

@piotrek thanks for the replies. 

If you have your CPR9-ea9 plugs still I’d install them before ordering and replacing a TPS sensor. I’ve had experience with 2 bikes recently that had a misfire due to those exact plugs (1 yamaha and 1 Suzuki) Maybe it won’t change your issue but it’s good to rule things out (for free). 

your reading dropping to .17k ohms around 1800 ohms may or may not be suspect depending on how your meter displays/auto ranges the results: however that’s good info. Concerning is that the other sensor doesn’t have that same change in measurable value, which points to it being possibly compromised. 

“arm chair” diagnosis is challenging on our end for sure. 

nice charts btw. Remember that with Yamaha TPS sensors 2 of the wires always equal 5 volt reference signal and ECM “clean” ground (blue L and Black/blue B/L if memory serves). The other 2 are the “wiper” signals back to the ECM.  (Just thought typing that out for you to read might help simplify the system for you, pardon me, if it annoys you...)

-Skip

Edited by skipperT
  • Thanks 1
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×