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Viper Dad installed the Acceleration Sensor and calibrated it this weekend. No luck. Didn't resolve the surging at all. No charge.

So where it stands now, all vacuum lines cleaned and inspected, TPS installed and calibrated, APS installed and calibrated. Still surges in that RPM range.

Any thoughts on what's next?

This is an odd situation, most of the issues elsewhere are surging or hunting, etc. are at idle speeds, not at 3-4k rpm. All the normal fixes wouldn't seem to apply..... so, bit of a wild stab here.... do one thing at a time, not several things at once so we can nail this down for future reference.

1. Several issues have been because of a seemingly good but deteriorating battery.... do we know it is good, via a load test? FJR's seem to need a great battery and things happen it seems when they are "half done".

2. Spark plugs..... perhaps one is breaking down, still works for most conditions, yet perhaps at steady speed it's flaky.... does this problem occur with brand new plugs........ test ride please, but first.....
2b. While you're in there, check the coils aren't cracked/broken (from installing/removing the T-bar and insulation), and coil primary resistance (1.19-1.61 ohms is spec). One can test secondary resistance, terminal to spark plug adapter (8.5-11.5 kOhms). On older non coil-over, there was a resistor that may have corrosion...... don't have a coil-over in front of me, can you remove the guts from the spark plug end?

3. Have there been any further recurrences of error codes, and if any, what were they? Particularly interested in 11,12. Usually those are a bit flighty, not usually credible, but if the cylinder identification sensor is flaky...... I have a near new one here you can have if trial and error test desired.

4. When was last valve check done and were any on the low side? Kind of a grasping at straws thing, but if an intake valve is too big, ie, above max, might be an indication of carbon build-up.... not suggesting a valve check just yet, that's a bit of work....
One simple cheap thing to do is, go get Gumout combustion chamber cleaner, hook up 4 hoses to the TB sync locations, and in succession at 2000-ish rpm on a well warmed up engine, squirt some in each port.... use the whole can, and it should flake off any carbon on the intakes... potentially, this will let intakes seat better (yep clearances may become smaller). Before starting this, check the TB sync and make note where you're at. Then check sync after the carbon removal exercise and see if the sync changed... valve clearance changes will affect sync, so jes sayin' if it does change, then you maybe did get rid of some carbon.... re-sync, go ride, anything better?

Festus wrote: ↑Mon Nov 29, 2021 9:10 am Viper Dad installed the Acceleration Sensor and calibrated it this weekend. No luck. Didn't resolve the surging at all. No charge.

So where it stands now, all vacuum lines cleaned and inspected, TPS installed and calibrated, APS installed and calibrated. Still surges in that RPM range.

Any thoughts on what's next?

Man! This is so frustrating! What a mystery. Ray has come up with a few things to try. Best of luck Viper Dad. Just give him your bike Festus.

FJRPittsburgh wrote: ↑Mon Nov 29, 2021 5:59 pm

Festus wrote: ↑Mon Nov 29, 2021 9:10 am Viper Dad installed the Acceleration Sensor and calibrated it this weekend. No luck. Didn't resolve the surging at all. No charge.

So where it stands now, all vacuum lines cleaned and inspected, TPS installed and calibrated, APS installed and calibrated. Still surges in that RPM range.

Any thoughts on what's next?

Man! This is so frustrating! What a mystery. Ray has come up with a few things to try. Best of luck Viper Dad. Just give him your bike Festus.

I have no extras, you, on the other hand.....

Ray, thanks for the info. Brand new battery, installed a month or so ago. No changes from that swap. He did tell me that he put one new coil pack on some time ago. Said something about it looked dry rotted or cracked or something (I don't remember what he said, I don't listen when he talks), but he said he replaced one coil pack. I'm not sure when he did that and I need to ask him about it. I wonder if, by chance, it fits the timeline for when things started.

Valve check was done when we had the engine out 20,000 miles ago, maybe? Plugs replaced at the same time. No other error codes every show up.

Next thing I'd do is try a new set of plugs in case one is breaking down.... might be OK at idle (zero load) or under load (more current generated), but flaky at steady speed/coasting, load but light load.... I would hope it's that simple.
I had a cracked coil-over because I accidentally broke it during t-bar removal, wasn't oriented properly from the dealer/factory?.... luckily only cracked where the wire harness plugs in, I plastic epoxied it and it was fine.

At this point, I'm close to suggesting we just bring the 2 bikes together and start swapping parts until we find the issue. No sense in just spending money to replace sensors that are fine until we stumble upon the issue.

You're not there yet and may not have to go there.... easy stuff first, could be simpler than we know......
Which sensors you thinking of swapping that you think will make a difference?? Maybe we can help with that.

Peanut gallery time. Surging is generally related fueling. Sounds like you guys have done a good job of the intake side, what about the exhaust side. Aftermarket cans? Maybe a back pressure fluctuation owing to decaying packing. I've seen some pretty bizarre symptoms caused back pressure changes/resonance.

(Mimes shooting at ducks with a shotgun as they fly past)

Maybe the servo, Ray? Before that, I'd swap coils and plugs. Last resort, although pretty easy, is to swap out the entire throttle body assembly. At least then, it would isolate if it's something on the throttle body.

Bungie, stock cans, nothing has been changed on this bike, from the aftermarket performance side of things.

The servo is just a stepper motor being told what to do..... how to test a servo, well who knows, but it's working. ECU is telling it what to do, so what tells the ECU the info it needs..... The rest of the sensors on the TB's themselves.... MAP sensors, TPS, APS is about it.
Non-TB sensors.... intake air temperature (not likely), ignition pickup (not likely but maybe... they don't fail), cylinder identification sensor (possibly), 02 sensor (unplug it for a test ride?). Spark plugs and coils are higher on the list.... fuel pressure, maybe but not likely.

Just throwing this out as it seems we're all grasping at straws here. Reread this thread and just caught the "when we had the engine out" part even though I knew this before. What about the possibility of having pinched a wire somewhere during the reinstall? Possible sporadic voltage issue to a sensor or something?

BkerChuck wrote: ↑Wed Dec 01, 2021 11:17 am Just throwing this out as it seems we're all grasping at straws here. Reread this thread and just caught the "when we had the engine out" part even though I knew this before. What about the possibility of having pinched a wire somewhere during the reinstall? Possible sporadic voltage issue to a sensor or something?

With the TPS out of the picture, I would probably look at coil-over-plug and then the plugs themselves (At 20,000 miles, they are past due). Would give serious consideration for a fuel injector that is contaminated or otherwise not functioning optimally. These things are easily ruled out if you have a "donor" bike to swap parts back and forth.

I also like the notion of the pinched wire - especially if misbehavior dates back to major maintenance. Maybe check O2 sensor - unplug it and see if behavior changes...

Good luck!

BkerChuck wrote: ↑Wed Dec 01, 2021 11:17 am Just throwing this out as it seems we're all grasping at straws here. Reread this thread and just caught the "when we had the engine out" part even though I knew this before. What about the possibility of having pinched a wire somewhere during the reinstall? Possible sporadic voltage issue to a sensor or something?

I suppose it's possible, but it's been in use for 2-3 years since the engine being put back in.

Maybe the catalytic shit the bed. Sorry, I'm invested in the exhaust side.

The problem with swapping the TB's is you have multiple devices and won't know which is the problem... but TPS and APS are new, MAP sensor hoses clean.... but how's the donor bike?
Pinched wire at the right timing cover can cause issues, but I'd think more than at a narrow/specific rpm at no load.....
Doubtful it's the exhaust, you'd have more issues than that...
Yes a fuel injector could be an issue with not enough flow at no load.... one can go into DiAG, with injectors removed from the TB's cycle them individually to see the spray pattern.... or you could spend $100 and have them cleaned and come back with a flow report.

That was my advice Ray, have the injectors cleaned and inspected, but might try swapping coils off known good bike to that one and see if that resolves anything.

Step 1, try new plugs. Cheap. You need a spare new set anyway for down the road. Coils likely OK, do that next if the plugs don't fix it.

Wow. And I thought me and KrZy8 had mechanical sagas!

I saw only one mention of fuel pump. For all the diagnosis so far one of the easiest things one could do is borrow an entire gas tank from another FJR for a few miles. Fuel pressure regulator may have trouble regulating a steady flow. Trouble that isn’t noticed during changing demand.

I don't think there's much indication of a fuel pump/pressure regulator issue at this point. Symptoms would be different and more widespread, like losing power at higher rpms and accelerating.