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Discussion Starter · #1 ·
Hello fellow FJR owners.
I have a 2013 fjr that has recently started surging in rpm. It starts and idles fine but when I increase the throttle to about 2k rpm it surges up to about 4500 rpm. It does this in all gears.
I just replaced the aps (#12 in the parts diagram) and I'm still having this surge issue.

I completed the 24k mile service last fall including new plugs, coolant, oil, and throttle body sync.

Any suggestions? Should I remove the throttle body assy and replace the tps? Is the aps and tps interchangeable? (Could I use the old aps to see if it fixes the problem?)

Any help would be greatly appreciated!
 

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Well, my TPS started acting up at about 25,000 miles. It didn't act like that, though. It just stuttered a low throttle openings and was very frustrating trying to take off slowly or roll along at moderate speeds at very light throttle openings. I took it to the dealer to diagnose, and they told me it wasn't throwing a code, so it couldn't be the TPS. The owner of the shop said he couldn't just start replacing parts hoping to find the problem, and I said "Well, I can." Luckily, the TPS was the first part I replaced, and that fixed the problem.

FWIW, it can be replaced without removing the throttle bodies. It's a bit tedious, but it can be done. I won't go into it yet, but if you decide to go that route, post back here, and I or someone will tell you how we did it.
 

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FYI, there is one other 2013 I know with a surging problem, he's been through most everything and has replaced the TPS..... now thinking of replacing the APS...... hmmmmm. Bit of a mystery.
In looking at the wiring diagram, the TPS and APS appear pictorially to be different internally........ in the test section, the service manual shows different (albeit not great) differences in resistance values... I'm just going to say they are not the same.
I am wondering if the cylinder identification sensor is coming into play....
 

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My bike's idle speed was erratic, frequently racing but sometimes normal. The problem was caused by accumulated gunk in the coolant circuit for the wax motor, which adjusts the cold idle speed. I cleaned out the small diameter metal tube return line at the radiator, which was inhibiting flow of hot coolant that would activate the wax motor.

See Queensland Ken's postings at Cold/fast idle problem ..... Fixed

In my case, the metal tube return line at the radiator was fully plugged with hard crusty stuff. I used a piece of wire to gouge it out, and found that it extended about 1/4" into the metal tube. End of problem.
 

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That would solve a problem of the bike not coming down off fast idle....... this surging issue is in a higher rpm range, and I suspect there is an issue with a signal the ECU is interpreting......
 
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Discussion Starter · #8 ·
I did a throttle body sync last year at idle. It needed some adjustment and I was able to get them synced at idle. I never check it at higher rpm. Could this cause the surging at higher rpm?
 

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Sync will have less effect at higher rpms, mostly will lessen vibrations a tad. I think the issue is electronic.....
 
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My reading comprehension is sometimes suspect so just for my own clarification - when you say 'surge', is it a jump from 2k right up to 4500 rpms? Or is it surging up and down between those two points? And once up at 4500 does it rev smoothly up and down above that? Lastly, this came on just this year and not immediately after your 24k service in the fall, correct?
 

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Discussion Starter · #11 ·
Big,
Yes it shoots up from 2000 to 4500 even though I'm not twisting the throttle any more. It stops out at 4500 and then will go up if I twist the throttle more.
 

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I believe the surge on the other '13 isn't abrupt like you have, so let's call yours a "jump" in rpm. TPS usually hasn't caused this, so I'm casting a vote to replace the APS. ECU is seeing wrong throttle position and wants to raise rpm to suit what it is seeing ??
The other '13 has a problem holding steady throttle at any rpm, bucks and surges.....
 

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Discussion Starter · #13 ·
i replaced the TPS with no change in the rpm jump. i ordered a new APS. it looks like replacing the APS is a bit of a job and its starting to get expensive throwing parts at it. Do the TPS and APS have redundant circuits? there are 2 readings for the TPS and APS in the DIAG mode, and it would make sense to have some redundancy built into a safety critical electronic system like this. they are both showing good signals and smooth increase as i twist the throttle to WOT. i am starting to doubt that its an issue with the TPS or APS.
i was tinkering around last night and noticed a smell of fuel when i was fiddling around the throttle bodies. i took the air filter out this morning and noticed the fuel smell again when i took the filter out. if an injector or two is leaking or wont close off completely, would it make the rpm jump up? it would be getting more fuel after all. then, would this cause a secondary issue where the ECU is sensing that its running too rich and introduce more air to compensate, also increasing the rpm?
 

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You can pull the injectors without removing the TB's, and activate them via DiAG, but jeez, not thinking it's injectors. Leaky injector would be a problem all over the rpm range wouldn't it?
If it got more fuel, the O2 sensor is the next thing to catch that, but I wouldn't think any drastic jumps in rpm would result from that either.
No redundant circuits in the TPS or APS, just two separate resistor boards in each that seem to have differing functions. See pic of forensic analysis of TPS, see what you can theorize.
The 4 wire harness terminals are at bottom in the pic.


78573
 

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Idea from another sandbox.... Not sure if this will work, but try it.... set cruise under 2000 rpm where your issue is (say 3rd gear), then bump up in slow increments to see if you experience the jump anywhere in the 2000-4500 range. This may take the APS out of the picture...... note cruise only works 30 mph or more, likely can't stay below 2000 rpm in 3rd (2300?).

Addditional question, when you decelerate from 4500, and try to hold say 2500 rpm, what happens?
 

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Additional question..... what happens if you try to hold steady throttle say 3000 or 3500 rpm... does it jump or buck up and down? Might want to try it in Touring mode to desensitize the throttle a bit?
 

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Ive been following this with interest. My 13 did exactly this from day 1. I tolerated it for a long while trying to understand it. Dealer had no clue, which will surprise no one. TPS replacement cured it. Im thinking because mine did it from new, your "new" TPS might be bad. Wouldnt be the first time a new part was faulty out of the box !
 

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Discussion Starter · #19 ·
I'm gonna try to get out and test this tomorrow.
the more i research, it seems like this might just be the result of emissions restrictions. i spoke to Ivan about his ECU flash and he sounded like this was typical and would be solved with his flash.
 

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Well test it before throwing money at it. Unless your issue is different that I understood it (a jump from 2000-4500 rpm), seems there's an issue needing solving that a flash won't fix. If you can better define your issue, that would be great for understanding........
 
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