More 2-4K surging questions

[race24x]

I did a search and really didnt find anyone that found the holy grail of answers for this. My bike like many others is surging very badly from 2-4k. I have pulled the screens froim the injectors, cleaned the screen in the beggining of the fuel pump, replaced the fuel filter, and spark plugs. I had the dealer set the valves and TPS as well as synch the throttle bodies. I tried unplugging my PCII. None of this helped. I am at the point where I believe it may be a bad coil or a leaking spark plug boot as it feels alot like a cylinder drops but only when you are trying to maintain a steady RPM in the 2-4k range. Accelerate and it is fine decel is fine. I do also occasionally get a little bump or skip or hesitation at idle if it idles for a long time. Just once in about 30 seconds like it loaded up and missed one fire. I am going to try dielectic grease in the boots and wrap some electrical tape around the outside of the boots. I am worried abotu a cracked coil or something like that. One other thing that really haunts me is that coold engine not all the way to full operating temp it runs perfectly. This only happens when fully warmed up. Do these Busas have an open and closed loop system? I was a GM tech for 7 years. I understand the basics of fuel injection.

 

[Professor]

US spec bikes 99-07 are open loop. Some non-US models are equipped with O2 sensors and are closed loop.

08-Present all are closed loop.

 

[race24x]

OK so that is a dead end I kind of figured due to lack of O2 sensor, but its weird that it runs well until hot. I am going to try the old water spray on each coil to see if I can force it to skip that way. The other thing I was considering was a faulty injector. Maybe partially bad?

 

[Professor]

Problems like that can be difficult to track down without using a dyno and test equipment.

Even a faulty side-stand switch can cause something like that.

 

[race24x]

I can bypass that swith I beleive by jumping them together. A friend has a dyno, but I didnt think that would help find the issue. IF its fuel or electrical it will show up rich in the AF graph right?

 

[Professor]

I may have misunderstood the original problem. I assumed it has been tuned and nothing else has changed since the tuning. I also thought it was intermittent because of the “occasionally get a little bump”. The factory mapping should be a bit richer until it has warmed up. Also this is typically where they are a bit leaner from the factory to meet emissions. Surges are usually from lean conditions and you usually see 10-15% or so fuel added in 2-4K range at lower throttle settings.

Since it repeats with no PCII are you sure the PCII is working correctly? It has been a while, but if I remember correctly you cannot pull the map from the PCII like you can the PCIII. Therefore you cannot see what is loaded, you can only send a new map. Hopefully you have the map to write back to it.

The main reason I thought a dyno would be helpful would be to get it in the exact situation where the problem is showing. Run it at a light load between 2-4K and monitor the engine to see what is happening. Is the injector pulse width dropping out, what does an ignition scope read during the problem , what happens to the O2?
Fuel pump and screen problems usually show up a higher rpms.

I have heard of side stand switch not making good contact and the harmonics at certain steady rpms cause the switch to open. Yes, jumping it would be good way to test. However, I may have led you the wrong way if it constantly and exclusively behaves within that rpm range.

Electrical will usually show up rich. Fuel would be depend on what it is happening. Injector sticking closed, leaking ect.

 

[race24x]

I am not sure about unloading the map I have never tried that. I was going to try and unload the map and set the TPS and then load the map back in This was recommended by my freind with the dyno. To me it feels like one cylinder is stuttering in the 2-4K range. only when the engine is warm. Then it really feels like a surge because of the power loss and gain back. Full throttle it goes great. If you load it way down to 1200 and full throttle it soetimes will hickup a few times and then go, but above 2K full throttle is great. Its weird because usually more fuel and load usually brings an electrical skip out. I am going to try the kickstand to see if it helps. THen wet each coil down cover them with electrical tape and grease inside and replace plugs. This issue just came up one day and got a little worse and now has been about the same.

 

[thinblueline]

im having the same issue did you ever track down the problem?

 

[snowprophet1]

Same problem right now. Just ready to start troubleshooting. If anybody found the fix, we're all ears!!

 

[Hunter787]

Yeah, mine was a loose spark plug, how it got loose is still a mystery, but that was it.

 

[BusaWhipped]

Mine surges in that RPM range in 1st-3rd gears because I have it tuned for optimum gas mileage in 6th gear on the highway. The lower gears are running lean because of the differences in the fuel maps for which the PC can't account. Below 2K and above 4K I'm tuned for power.

 

[snowprophet1]

Mine is an '05. I bought it knowing the motor was swapped w/an '03. I never rode it 'til now. The guy even told me it had a hesitation when you go to leave at a light. He took the power commander out of the loop, but it stayed the same.
Now I finally got to ride it. Drained the old gas that had sea foam in it when I first bought it in December. Put fresh gas in it, and no better. The more I rode it and the warmer the outside temp, the worse it got while pulling out from a stop. Since I knew the engine was swapped, I wondered if the tps was ever zero-ed out, reset, or calibrated, since the computer and new motor w/different tps was not matched? So I jumped out the plug to get the codes, and sure enough, it was off by a little. I set it and WOW is it smoooooooooth now! No problems and I LOVE IT! Now that I know there are no problems w/it, the turbo can go on! (after I put my Vmax back together so I can still ride if I have to wait for any parts!)