Miss/Stumble just off idle ....

[HellFire]

In the last few days I've had a small problem with how she runs accelerating slow when coming off idle. Idles fine, runs fine, but stumbles like a miss or a fuel issue at the same throttle/rpm spot every time. I haven't looked into it yet and probably won't until I have a chance to run another tank of gas through it (gonna go get some alcohol free stuff Budman found). Just thought I'd put this out there for you guys to see and tell me if something similar happened to you and what you found/did to correct it.

Since it happens in the same spot each time, I was hoping it wasn't a TPS sensor and will try swapping the two front to rear just to find out. I guess I'll have to finally break down and fire up the TuneECU to reset them afterward. Maybe I should use it to check them first? Will the tool show one that has a dead spot or bad value reading?

Maybe the PCIII is set too rich just off idle? Might be a good idea to re-check the map for something off at that spot on the chart?

Anyway, open for ideas ... fire away.

 

[Gothlander]

Check coil wires are snug (can vibrate at certain revs), CAS may need cleaning, GPS may be swapping maps when it should not ? Plugs could be fouling with **** fuel.

 

[TOMCAT]

I had similar problem,could have sworn it was fuel related. Cleaned and crimped/tightened female splade fittings on wiring to coils..Problem gone.

 

[HellFire]

Never thought of that ... very well could be a specific vibration frequency making a poor connection at the same place each time. I'll add that to my check list, gracias.

 

[Captain Bob]

You may have a bit of water in the tank causing the stumble. I have seen this on a couple of my cars as well as other bikes. Put a bit of dry gas in your tank and if it is water, the problem should go away immediately. I am told the ethynol seperates the water from the fuel causing this problem. This occurs most frequently on my Ford Focus. The stumble is usually in the same are as well. I put drygas in the tank and ...... voila! problem is gone

 

[HellFire]

Products like Drygas and Heet ARE alcohol ... it doesn't separate water from the gas, it picks it up from the bottom of the tank and mixes it with the fuel.

Water + Gasoline doesn't mix
Water + Alcohol does mix
Water + Gasoline + Alcohol mixes small quantities of water

Budman said he found an Alcohol free gas station nearby, I'm going to try to find it and put the bike on the wagon for awhile anyway just to see what a difference it makes.

 

[HellFire]

Just for grins on the way back from the store, I used the manual settings on the PCIII to reduce the low by two bars and the mid by one bar. I couldn't get it to stumble at all on the way home and it actually had a little exhaust pop on decel as a result. It looks like the low end fuel trim was a little too rich (might be a tad lean now), must have to do with change in temp/fuel/mood . I'll have to plug it into the laptop and compare the change in the charts to see what's going on.
Hmmmmm...

 

[gwilliams290]

My first thought was water in the fuel. Where it may have come from is immaterial, bad gas, condensation, whatever. Water is heavier than fuel and will settle at the bottom of the fuel system making the early stages of running have a miss or stumble until the water goes away.
Your analogy of mixes is correct and the alcohol mixing with water helps the "smaller" quantities of water to be burned off as opposed to just running through the system and producing steam from the heat. White smoke.
Interesting about the PCIII fix. Better to run fat than too lean.

Side note, just finished my dyno run and now she's dialed in. 196 HP and 202 lb/ft of torque. Turbo's can be wonderful things. Smooth all the way up and down.

 

[Timbo]

Had a similar issue with mine after changing exhausts for a home spun system. At around 10% throttle it would miss and splutter so bad that if you held it, the bike would stop.

The R3 has an adaptive ECU and it can adjust itself to the ambient conditions. I say this as you mentioned a change in temp, this is one of the factors.

To reset it, I used TuneECU and there is a radio button "Reset Adaption", double click it and the fuel pump, injectors etc will all start clicking, when it says ResetApaptionDone in bottom bar, try it out.

There is also a manual process. You start bike from cold, NO THROTTLE, let it warm till the fan comes on then leave it for another 12 mins, though some say up to 17.

But try all the simple stuff first

 

[HellFire]

I manually leaned the PCIII low band two bars and the mid one bar. Must have been a tad rich for the heat, all is well again.