Random Power drops while riding? - Yamaha FJR Forum : Yamaha FJR Owners Forums
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post #1 of 28 (permalink) Old 06-25-2020, 07:05 PM Thread Starter
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Random Power drops while riding?

-SEE EDIT- Code 19 resolved
Hey everyone, hope someone can help me out... My bike is randomly cutting out at various RPMs, see below for changes
I recently acquired an 08 FJR, and have just recently got it up and running and road legal! Hooray!
Except today I did some things and now its not running proper.

The original owner had a PC3 on the bike, but I had removed it initially trying to get the bike just operational.

Today I did the following :
  • Reinstalled the PC3
  • Removed the O2 sensor
  • Removed the PAIRs (all the air line tubes, capped off each valve and air box)

Initially I ran the "Smoothness" map I found online, but after experiencing the cutoffs I tried the stock map and it still is doing this albeit slightly less.

The symptoms are like it is completely losing fuel randomly, sometimes its at take off, sometimes just cruising at highway speeds (a scary surprise initially) and at one point the bike totally cut out, no power and wouldn't start momentarily stranding me on the roadside. A brief pause to google the issue and the 19 diag code I saw, it eventually started and I limped home. I read the "19" could be ECU trouble, so back to the PC3 as culprit.

Any ideas?

Do I just need to pull out the PC3 and reinstall the O2 sensor?

Thanks in advance !


If you are having this issue or similar, feel free to read through the posts, but I believe mine has been resolved as a SIDE-STAND SWITCH issue,
I bypassed the switch at the coupler connection on the left side of the fairing, using a small screw to jump the 2 metal connectors, and using electrical tape to secure it in place, completing the circuit.

*Note that this disables this safety feature of killing the bike in gear with stand down, BUT its not very safe if it is sending false signals to the ECU and cutting fuel on the highway is it?

Perhaps I will replace the switch unit in the future, but for now I simply wanted to take this new bike out on it's first proper ride in over 6 years!

Thanks to everyone who helped, big shout out to RayZerman as well and every other forum poster whose similar issues I read diagnosing this one.

Last edited by ThanksBarry; 06-27-2020 at 01:37 PM. Reason: Resolved Issue
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post #2 of 28 (permalink) Old 06-25-2020, 07:21 PM Thread Starter
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Side note, I had considered possibly TPS, but I cannot replicate the issue in Neutral , only under load in gear on the road. Any gear, any RPM, there is a chance it cuts out on me.
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post #3 of 28 (permalink) Old 06-25-2020, 08:15 PM
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A small amount of water in the fuel can cause this too.... ethanol phase separation occurs if it sits a couple of weeks or more, water goes to the bottom. The fix, Seafoam.. which is naptha and isopropanol... the isopropanol disperses the water far better than ethanol can.
Another possible cause, the MAP sensor... lift tank, insulation pad and remove the MAP sensor from the TB's, the black thing with two screws. To the bottom of it is connected a vacuum hose.... ensure the entire hose is clear of any waxy deposit, including the tip of the nipple on the MAP sensor. It's just a build-up over time, might help to ensure the hose has an angle such that it steadily drains, dunno.
PC3 might not be the issue, but sometimes they need power disconnected and rebooted. If it runs OK (O2 sensor connected) without it, and not OK with it hooked up (normall disconnect O2), then maybe it's the PC3.
PAIR system has no effect... it's just a system that passively lets oxygen into the exhaust ports to assist with unburned gasses.
Smoothness map will just burn more fuel, stock map from Dynojet should work OK... you can tweak it to add fuel at low rpms and it will help some, but the '08 up shouldn't really need a PC3. If you really want to fix it, go with the Ivan flash.
TPS can be an issue, really hard to diagnose properly since it can appear good in DiAG but not be. There is a way to backprobe the connector and monitor while riding... will have to look that up... let us know if Seafoam and MAP sensor cleaning doesn't work, meanwhile I'll try to find the writeup.
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post #4 of 28 (permalink) Old 06-26-2020, 06:46 AM Thread Starter
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So this is the first full tank of fuel I have put in the bike since restoring it, I filled it with premium pure gas, the no ethanol stuff. And I added some seafoam before the issue just to clean out the system (long story short the bike sat a long time, I restored it and it had briefly ran without this problem until today).

BUT I did wash the bike prior to riding, perhaps some water got down in the cap?!? That would make sense I guess though I worry about riding in the rain. I will keep the post updated as I try new things, might try removing the PC and reinstall the O2 sensor just to check if the issue persists today with those, that would really sell the water in the gas as the cause.

if anyone has any PC3 maps they would want to share I'd love to try them, I only have the ones dynojet offers plus the smoothness one.

Appreciate y'alls help!
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post #5 of 28 (permalink) Old 06-26-2020, 07:27 AM
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Barry, one thing I would check as well is the gas tank vent, make sure it’s clear & can vent properly. Being that you say the bike sat for years little critters like to build nests in the vent and I’ve seen it cause exactly what you’re seeing. There’s 1/2 of it going into the tank which is that little red rubber thingy that the cap mates to and the other 1/2 is in the tank itself. Both need to breath freely. Let us know what you find.

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Ride more,, worry less !

Last edited by passx; 06-26-2020 at 07:38 AM.
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post #6 of 28 (permalink) Old 06-26-2020, 07:59 AM Thread Starter
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Thank you yes that's actually one of the things that had changed since this problem arose, I had initially forgot to put the rubber venting hoses on the fuel tank.
I put them back on the 2 nipples at the back and ran the hose line down, I forgot to mention that was something that changed too, the line was clear and had actually leaked a bit of gas while the tank was off before I put the tank back on after installing the PC3.
Interesting, I hadn't considered something seemingly inconsequential to cause that issue...

So recapping changes made (it ran one day without this issue before these were done yesterday)

PAIRS removal - most likely not a cause

PC3 install - shouldn't be an issue, will try removing in a bit to verify

O2 sensor removed

Fuel breathers put back on tank

Adjusted the warm idle RPM, it was low about 900 and stalling I raised to just over 1000 and that seems much better at idle

I will also check the MAP sensor while I'm in there as suggested, will report back.

Another thing I've considered is doing throttle body synch? Not sure of any symptoms of them being out of synchronization, going to ask the local bike club if any members could spare one
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post #7 of 28 (permalink) Old 06-26-2020, 08:14 AM
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Crud in the fuel line at the screen?

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post #8 of 28 (permalink) Old 06-26-2020, 08:18 AM
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Continue to adjust your warm idle up, 1100 is much better. Can you tell if the Barbarian Mod has been done? Normally the '08 and up don't need a PC3, I suspect it was installed originally to mask rather then repair another problem. I'd remove it and go from there.



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post #9 of 28 (permalink) Old 06-26-2020, 08:49 AM Thread Starter
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I will push the idle up a bit more, and I highly doubt any mod has been done, the original owner was an older fellow who was 100% by the books, always dealer serviced (read he was wealthy and would rather pay a pro for any services). Unfortunately he is no longer with us so I cannot ask him any questions, but he kept a log book and I've read through, only basic maintenance and scheduled services/recalls performed. I will however verify again that the ECU has not been altered.

As far as fuel line crud, I'm fairly certain it is clear, is the screen you mention Jim the one in the fuel pump? The pump is brand new, while restoring this bike the tank had sat for years partially full of gas, it had rusted bad, I totally cleaned it out using electrolysis and sealed with POR, and the original owner purchased a new fuel pump (it was needed the old one was full of rust) and I installed it after finishing the tank, so I know its clean as well. (Maybe i will make a post outlining my procedure, I've done it on many steel bike tanks and it works very well!)

Since everyone agrees the PC3 isn't really necessary I will remove it and go back stock, honestly like I've said it was fine until I put that in!!!

I let the bike idle the past 15m just to warm it up and get the dew off, and it died while moving it to my workstation, so at this point I hope increasing the idle will stop that.

Will continue to update thread as I progress, Thanks again everyone
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post #10 of 28 (permalink) Old 06-26-2020, 11:36 AM Thread Starter
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Ok... Update after some burnt hands and cursing.

Removed PC3 & reinstalled O2 sensor. Checked MAP vacuum line, they're all clear, checked fuel tank vent, it was partially clogged but I cleaned it out and its open.


In fact I got stranded down the road from my house, and consistently was shown "19" code as it refused to start. It turned over and briefly ran then died. After sitting briefly it did start and run and i was able to get home.

So from what I remember that code is either the kick stand down while in gear, or just ECU error.

I had checked for the barbarian mod or any loose wiring and made sure i pushed the plug in securely, and cleaned off the kickstand sensor button, but wasn't able to disconnect it yet.

Anyone have any other ideas? is something just flat out wrong with my ECU??
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