'99 low rpm miss

txfastesttoys

Registered
I have a 99 and about year ago it developed a miss when the rpm gets to 2800 and quits at 3500. It does this most of the time but not all. When I got the bike it already had the full Ti. Achropvic exhaust, the breather was modified and it had the Power Camander on it. It allways ran great exect for a lean stumble at the lower RPM. I lived with the stumble for a year. But then it developed this miss. The miss got alot worse sometimes feeling like it was dropping a couple of cylinders over all Low RPM. I took it into a local shop and he said one of the coils went bad and he replaced it with a used one. At that time I had him tune on the programmer a little bit to help the stumble out which he did make it a little better. A few months after riding it four or five times the miss started coming back. I wanted to take it back to the shop to get the miss fixed and have him put it on the dyno to a full fuel map done on the Power Camander. I wanted to change all the coils so I bought four used coils off of Ebay. I took the bike over to the shop he changed the coils for me and put it on the dyno for tuning he said he was able to get fuel map done and it made real good power 168hp but the freaken miss is still there at the same RPM. The lean stumble is fixed. But the miss. It does it almost every time it goes through that RPM range. The shop guy said he was baffled is not sure what it could be and if he is baffled,I sure am. I am sure hoping someone on here could help me out so I don't have to spend a bunch of money trying to chase the problem down. Sorry for being so long winded, I just want to give all the facts to get the best help.
 
Clean the fuel filter.
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Double post.



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I would like think it would be that simple and you might convince me that it is. But It only misses Between 2800 and 3500. Every were else it runs great. It never seems to be starving for fuel. Once it gets above 3500 it hauls ass all the way out the back door. It only misses when driving around nice and calm and hit the that same RPM range.
 
If the original pump is still intact,there were some issues with the pumps on the 99-00,this has been well documented,I think it may have even been a recall.Check the filter and or have the pump replaced,maybe try some fuel injection cleaner/conditioner.
 
That's sort of what my 99 does intermitently. Hopefully soon it will be 'what it used to do'! My mechanic 9the 3rd to work on this issue) found that it had a bad rectifier and was putting out 14 volts at idle and then would drop at about 3000 rpm to 12 and then get weird after that. The ecu's dont like having their voltage messed with like that and the pc mapping gets screwed up too. I'll know in afew days if the bad recitfier was the problem.
 
Sounds like my problem too:

I just bought a '01 Busa with K&N filter and 2 Carbon Can Co Stainless pipes.
The problem is, I am getting a litle bit of roughness/hesitation at around 3k - 4k revs. Feels like the fuelling is not right, maybe. Anybody else have this problem?
Could it be something else like a dodgy spark plug or injector?

Let us know how it goes.
 
Re; Low rpm miss that we are both experiencing: The new rectifier is in and for the first time the bike is responding to changes in the pc2. I was going to sell the spare pc2 I had but it is fried. I'm a couple of days away from loading the original map back into the pc2 and I should be back in business. I'll let you know as soon as I do. For now, I'd check your voltage for stability.
 
Hi,

My rough running problem has been solved. It was water in the tank. Must have got down into the fuel pump and filter. Anyway she's pulling away fine now. Thanks for the help.

Tony
 
Check the TPS/Throttle Position Sensor.
If it's off it could cause this problem...
There is a proceedure in the shop manual to set it with the digital display...


David
 
Update: it wasn't the rectifier, or the stator. Both are replaced and it's not better. Wiring harness might be it. Oh, this isn't going to be easy. By the way, my stator was shot, rectifier as well.
 
I have the same problems at my busa-99,have check everything,new fuel filter,clean fuelpumpand,all censor i have check nothing wrong wid anything,for me it started after small airbox mod and pairvalve remove???
 
Ya well I have been changing just about everything. Just as I read that yours started missing after you modified your airbox. I am in the process of changing my airbox back to stock with a K&N filter and put most of the vacuum lines back on but I am not going to hook up the air injection yet and see what that all does.
 
Hello,in the airbox there are 4 tratten 2 long and 2 short,gonne to take away 2 long tratten and mont on 2 short, (4 short tratten ) and se whats happens. I have the small airbox mod.
 
I have had the same problem with my 99 busa it started about a month ago
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after reading your post txfastesttoys and thinking about it i came to the conclusion it had to be fuel related, however I did notice it was ok while the choke was on, After playing about a bit with the choke lever I have found that if I leave the chock on about a quafter not enough to rase the revs the problem stops
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I think it is very odd that all of the problems are happening on 99 - 00 models. I just bought one last week and have the same problem. Sounds like a bad plug until it warms up and gets higher rpms. Just replaced the plugs and put new gas in it but still nothing. I refuse to let this gremlin win! No FI codes or anything just runs crappy at low rpms with a load on it (not that bad sitting still revving bike)
 
My -99 still missing at the low rpm try everything but still have the same problems.When the bike whas new i can hear that the bike have low rpm miss but not so strong to that whas interrupt,but when after mods its gegin to be stronger rmp miss.
 
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