Need Help FZ6 S2 Misfire at Idle and up to 3k on partial throttle

[Si1973]

Hi again all,
After having solved my top end problem 2 weeks ago by changing the plugs, fixing a vacuum leak and reassembling my fuel pump correctly, the bike has just started hesitant starting again and a super lumpy idle and up to about 3k rpm. Road speeds it rides perfect and performs as it should.
I replaced the battery and it's still the same.
Misfire and super lumpy at idle and partial throttle, with the "gulp" you used to get with Carbs when cold.
Worse when cold, but still there when warm.
The "gulp" is worse when cold.
The misfire is there warm and cold.

Does anyone have any obvious thoughts please?

Thanks,
Simon

 

[TownsendsFJR1300]

Does the RPMs seem higher than usual (like a cold start) and
remain slightly higher and stinking of richness?

 

[Si1973]

No, I don't think so.
Just ridden it pillion up with a loaded back box and returned 62mpg.
Goes like it always used to above 3k to eager redlne.
Just idles like crap and misses up to 3k.
No idea.

 

[Gary in NJ]

Sounds like there is still a vacuum leak. Also, a throttle body sync may help.

 

[Si1973]

Sounds like there is still a vacuum leak. Also, a throttle body sync may help.

Cheers,
How do you perform that sync please?

 

[Gary in NJ]

You use a carb sync tool. I have and use a dial type, but the consensus on the forum is that the liquid types are easier to read.

Its a very easy process, but it usually follows a valve lash adjustment. How many miles/km’s on your machine? The valve lash should be checked at 25,000m/40,000k.

 

[Si1973]

23k, but all this just started suddenly.
Valve clearance increase would have been gradual, surely?
You don't think it's fuel pump related?

 

[Gary in NJ]

A failing fuel pump is more likely to show signs of failure at high rpm, not idle.

We generally don’t notice things that degrade over time, only when they stop working. It’s the old boiling a frog parable.

When you can’t pin point the source of a problem, then it becomes a process of elimination. Since the bike isn’t throwing a code you will have to diagnose the problem one step at a time. I would start with a FSM diagram of the vacuum system and confirm that every hose is accounted for, and properly terminated. If any hoses show signs of dryness or age, replace them. You can use an unlit propane touch to survey the vacuum lines. If you come across a cracked/damaged/disconnected hose, the rpm will briefly return to normal.

 

[Si1973]

A failing fuel pump is more likely to show signs of failure at high rpm, not idle.

We generally don’t notice things that degrade over time, only when they stop working. It’s the old boiling a frog parable.

When you can’t pin point the source of a problem, then it becomes a process of elimination. Since the bike isn’t throwing a code you will have to diagnose the problem one step at a time. I would start with a FSM diagram of the vacuum system and confirm that every hose is accounted for, and properly terminated. If any hoses show signs of dryness or age, replace them. You can use an unlit propane touch to survey the vacuum lines. If you come across a cracked/damaged/disconnected hose, the rpm will briefly return to normal.

Had the airbox off again this morning and all hoses are connected and perfect.
Put a carb balance vacuum ( really old style one ) on each intake and they all pulled similar level vacuum closed and open throttle.
Really strange.
From idle if you snap WOT and hold it there is just coughs like mad and takes a few seconds to clear it's throat and then it's away perfect again.
I've increased the idle speed a bit in an attempt to get it to start more readily.
Maybe I'll have the plugs out AGAIN and just double check I've got them at 0.6mm + a little gap, but sure I did.
Going to take her for a ride now and make sure the top end is still there after this mornings dislodging of things.
No error codes, no engine lights.
Good fuel with no additives, stock air filter back in. ECU flash.
God knows

 

[Gary in NJ]

So I gonna say that an off idle bog (maybe more of a hesitation) from idle to WOT is normal…because that’s not a normal mode of operation. If there is a roll-on bog…that’s a problem.

Can you provide a video of what you are experiencing?

 

[Si1973]

So I gonna say that an off idle bog (maybe more of a hesitation) from idle to WOT is normal…because that’s not a normal mode of operation. If there is a roll-on bog…that’s a problem.

Can you provide a video of what you are experiencing?

Can't send the mp4. Do you know what format the forum accepts?
I've just put the K&N back in and took her for a rip. Top end absolutely fine to redline all gears ( couldn't try 5th and 6th obviously ). Also tried letting it go to like 15 mph in 6th on almost stalling and then cranking open, the same splutter is there and you roll back throttle until it eventually clears itself after a second or so, then it's clean pull up through the revs.
You don't notice any splutter or hesitation when you go gently on the throttle from idle speed on the road in any gear.
No gulping at any other rev range.
I just hate the fact it doesn't fire up like it used to and idles rough.
It was never like that.
Worth pulling the sparkies AGAIN and checking gaps and burn colours?

 

[Motogiro]

Could be a TPS issue. As well as air pressure sensor and air temperature sensor. Those three sensors are also on the same ECU feed.
I don't know where the air cut off valve is located and whether it might have an effect at lower rpm in reference to a vacuum leak but maybe it's worth checking.

 

[Gary in NJ]

Post the video to YouTube and link it here

There is a test for the TPS in the FSM.

Maximum throttle position
sensor resistance
3.5 6.5 kΩ at 20C (68F)
(blue - black/blue)

 

[Si1973]

Thanks very much.
I'm losing the will and desire with it now.
Looking at Tracer 900
I have no way or time to do all the necessary tests.
The only option I feel that I have is to take it to a garage or yamaha dealer.
P*ssed off and don't know what to do

 

[Motogiro]

Thank you @TownsendsFJR1300
There is another easy test for the tps that might help you. At least do this test. There are no tools or disassembly required. The FZ6 readout can be put in diagnostic mode and you can read the tps numbers while rotating the throttle. Rotate throttle slowly and observe that the number change smoothly and do not jump around. If the numbers jump around, replacement is a good idea. If you haven't, check youe ECU plug to insure the pins are clean and have no corrosion.
I know this stuff can get frustrating but take a deep breath. The FZ6 is one of the best all round machines ever built.

Just be patient and tell her you love her.....

Throttle Position Sensor Issues (Are you Experiencing Poor Idle/Mileage, or Stalls?)

Depending on much crap/build up is in there, you may very well have to run a tank or two of it before you see any change in performance. I wouldn't baby it either... Please post your results and good luck..

600riders.com

Thank you @TownsendsFJR1300
To check the TPS values, you have to press and hold SELECT + RESET, then turn the key and keep them pressed for 8 more seconds.

It'll appear dIAg on the display, you can release them now. Afterwards use select until you see a d01 (Diagnostic Mode for the TPS)

Then it should read between 15 and 17 if the throttle is closed,
With the throttle fully open, it should read between 97 and 100.

If the values are over or below those I mentioned, the TPS should be replaced.

To leave the dIAG mode, simply turn the key counter clockwise.

 

[Si1973]

There is another easy test for the tps that might help you. At least do this test. There are no tools or disassembly required. The FZ6 readout can be put in diagnostic mode and you can read the tps numbers while rotating the throttle.

Throttle Position Sensor Issues (Are you Experiencing Poor Idle/Mileage, or Stalls?)

Depending on much crap/build up is in there, you may very well have to run a tank or two of it before you see any change in performance. I wouldn't baby it either... Please post your results and good luck..

600riders.com

Already done that. All is fine, 16 - 102.
Seriously thinking of giving up and buying a Tracer

 

[Motogiro]

Already done that. All is fine, 16 - 102.
Seriously thinking of giving up and buying a Tracer

But....Did you tell her you love her?

 

[Gary in NJ]

The Tracer is certainly a great bike, but so is the FZ6 - and the cost difference is significant. Bring it to a qualified mechanic and enjoy the money in the bank.