03 40th low RPM misfire

Hayapower

Registered
Thanks in advance for any tips..

So, 15k on the clock, ran fantastic up till and including its last ride a few weeks ago.
Today, started out running fine leaving on a 3 hour tour and about 10 minutes into the ride slowed to low RPM to make a turn,, slight roll on the throttle and got a buck/jerk. ..Only..
First thought was the wheel lost its grab, corner was clean though,, but repeated again after leaving the next stop sign. No issues with grunt and pulls hard n smooth right up to the top,, no FI light.
After a few hours it’s gotten worse ( can reproduce the misfire dragging the clutch ‘stationary’ adding in some throttle). Seems like it misfiring on more than one cylinder..
When it started the issue, seemed like only one hole was dropping out. Or was just a quick fart, then ran fine..
Plugs are still OE,, certainly a possibility and first check point, but given the rapid change in how it’s run in just a few hours, leads me doubt them. Fuel is clean, same tank as the prior ride when it ran fine..
Duplicating the misfire as noted,, it seems ignition dropout related since the mis is abrupt for the most part, clearly hearing cylinder contribution is lost and/or erratic.
Injector/s,, ignition, hard to tell.
It does idle a bit erratic, maybe a slight mis now and again, but RPM affected ranges are roll off idle to about 3k.. Anything after that, a bullet..
Any pointers or alike failures that the Busa’s enjoy?
 
Thanks for the Welcome..
Batt is new, couple months old, charging system spec. output.

Could possible be just plug/s gone south and sounds ignition related. The misfire is very predictable at a given throttle angle. Cylinder contribution is a very abrupt drop out just off idle closing in on 1500, meaning it kicks in n out directly in that range, and more of a random misfire up to 3k within one or two cylinders. Running temps do change the severity..
But be it either one or two cylinders, it’s not an overal random misfire, but sounds to be the same contributor/s. Like a disconnect on a COP has occurred, then plugged back in...
I’m 70 miles from parts, so I ordered a set of NGK IX. I’ll certainly give all related possibilities a look see.
Being the misfire is easily reproduced, should be fairly easy to diagnose, and double check for a fix...
First time it sputtered/jerked, my first thought was possibly a TPS since it was just off idle (had no roll on misfire) and smooth anything beyond that, now it’s grown to a misfire higher up in the band, gone beyond 3k, no issues to the top....
Thanks....
 
Thanks for the Welcome..
Batt is new, couple months old, charging system spec. output.

Could possible be just plug/s gone south and sounds ignition related. The misfire is very predictable at a given throttle angle. Cylinder contribution is a very abrupt drop out just off idle closing in on 1500, meaning it kicks in n out directly in that range, and more of a random misfire up to 3k within one or two cylinders. Running temps do change the severity..
But be it either one or two cylinders, it’s not an overal random misfire, but sounds to be the same contributor/s. Like a disconnect on a COP has occurred, then plugged back in...
I’m 70 miles from parts, so I ordered a set of NGK IX. I’ll certainly give all related possibilities a look see.
Being the misfire is easily reproduced, should be fairly easy to diagnose, and double check for a fix...
First time it sputtered/jerked, my first thought was possibly a TPS since it was just off idle (had no roll on misfire) and smooth anything beyond that, now it’s grown to a misfire higher up in the band, gone beyond 3k, no issues to the top....
Thanks....
Hi there, I have the exact same model, first thing I experienced were the symptoms you described. All I did was change the ignition coils. No problems now.
 
First,, Thanks for all the tips,
Looks like I tried to over diagnose this misfire, thinking something more in-depth for cause, but turns out it was just plugs.
Guess if I’d of followed the change interval, I may have escaped any issues.
I did ohm all the coils P/S before receiving the plugs and they were all spot on. Plugs looked like new, and hard believe one was blown’n out down low.
I installed a set of NGK IX and it runs fine..
 
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