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Discussion Starter #1
Hi All,

Quite interesting one.

When bike is cold I have zero issues
When bike is warm it keeps stalling on idle. Revs drop to 700- 600 and it stalls few seconds later.
When I want to strat warm bike I woudl have to open the throttle a bit
Everything goes back to normal when bike is cold.


I'm reading about TPS issues , anything in particular I can do / check rather the buying new sensor?

Jay
 

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Jay, first check the MAP sensor vacuum nipple and the vacuum hose for any waxy build-up, that can cause that kind of issue. On Gen3-up, there are two of them on the throttle bodies, black with an electrical connector and two screws holding it.

TPS can be hard to diagnose, but first have to ask how many miles on it? If the above doesn't fix it, then perhaps TPS is the answer. Any stored codes? (You'll need an OBD reader and harness).
Also be aware there is an Accelerator Position Sensor, very similar to a TPS but under the right side of the throttle bodies... extremely difficult to get at, haven't heard of too many failing there, thankfully.
Unfortunately, idle speed is ECU controlled with throttle by wire, so no adjustments can be made.
 

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I have been told the "coil overs" can do similar. Work ok when cold then "open" as they warm up. I believe they are mitsubishi brand. They are used on many Yamahas. I was told by a cycle mechanic the average life on them is 25k-40k. How many miles do you have?
 

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Temperature sensor can do the same thing by flooding the engine. Do you have any blacker than normal exhaust smoke right before shutting off?
 

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At 55k, it could be TPS, but you can also have build-up in the MAP sensor port... check that first, it's a freebie.
Temperature input can have an effect, but if fast idle is coming down to normal, then it's likely working ok... rare to have a temp sensor issue.
I'm not up on coil overs or their life. Dunno if they have a similar resistor to normal spark plug adapters that might need a refresh... need to look up the spark plug end to see if you can remove the resistor and freshen up.
 

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Discussion Starter #7
At 55k, it could be TPS, but you can also have build-up in the MAP sensor port... check that first, it's a freebie.
Temperature input can have an effect, but if fast idle is coming down to normal, then it's likely working ok... rare to have a temp sensor issue.
I'm not up on coil overs or their life. Dunno if they have a similar resistor to normal spark plug adapters that might need a refresh... need to look up the spark plug end to see if you can remove the resistor and freshen up.
I'll make a start on MAP sensor tonight. Any advice how to get this cleaned?
 

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Discussion Starter #8
Stripped everything down,

All vacuum lines look like new so is the MAP sensor.
I also replaced spark plugs just in case and start it up.

No problem at all fast idle and then revs settled at 1100-1050. I ran it for 5 min, turned the engine off and restarted straight away. It started up but revs were around 500rpm but crept up to 1000ish and stayed stable.

So I'm back where I was. Wanted to rotate TPS but can't access screw closer to the frame. Do I need special bit or tool ?

Any ideas what should I do next ?

Jay
 

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just replaced MAP sensor on my '11....mine tested fine but failed.....would start up and throw code or go to rich....your problem almost acts like an injector is stuck partially open...personally I would run a little fuel system cleaner thru a tank and see if that helps
 

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Discussion Starter #10
just replaced MAP sensor on my '11....mine tested fine but failed.....would start up and throw code or go to rich....your problem almost acts like an injector is stuck partially open...personally I would run a little fuel system cleaner thru a tank and see if that helps
Happy to put some seafoam in however I'm very intrigued and would like to diagnose it properly
 

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If you did not notice a waxy build-up on the two MAP sensor nipples or in that end of the hoses, then you are likely good.
You can look at percentage throttle in your OBD readout, and take a guess how that relates to TPS settings from 0-106. Normal TPS setting is 12-21 at closed throttle and 97-106 at wide open throttle, keep in mind that is with prior model diagnostics where you can get a direct readout. Your OBD will likely read out in percentage of throttle.... basically, any change you make should be some kind of correlation to that.


Tight access to the screw... hex bit might be a bit long, dremel it shorter if need be and use a 1/4" wrench to turn it bit by bit. All I got there.


I hear you with one thing at a time. I'd have put Seafoam in it at the outset, or occasionally use it all the time. However, I think the problem is elsewhere.
 

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Discussion Starter #12
If you did not notice a waxy build-up on the two MAP sensor nipples or in that end of the hoses, then you are likely good.
You can look at percentage throttle in your OBD readout, and take a guess how that relates to TPS settings from 0-106. Normal TPS setting is 12-21 at closed throttle and 97-106 at wide open throttle, keep in mind that is with prior model diagnostics where you can get a direct readout. Your OBD will likely read out in percentage of throttle.... basically, any change you make should be some kind of correlation to that.

Tight access to the screw... hex bit might be a bit long, dremel it shorter if need be and use a 1/4" wrench to turn it bit by bit. All I got there.

I hear you with one thing at a time. I'd have put Seafoam in it at the outset, or occasionally use it all the time. However, I think the problem is elsewhere.
Thanks bud. I don't feel the problem lies in the fuel supply, however seafoam won't make any harm. Funny thing is that when you start the bike up from cold it has bang on fast idle and revs gradually drop and settle at touch above 1k when bike gets warm. When you turn it off and on it will either stall straight away either start at 500rmp and Will slowly creep up to 1k again.

MAP Sensor looks like new with zero buildup whatsoever.
 

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Discussion Starter #13
Took fairing off to have better access to the side if the engine. I saved some diagnostic data from cold to hot and then on restart. You will see rpm stays at 711rpm and goes up.

Checked TPS an accelerator position sensor, readings look reliable.

I'm properly stuck
 

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Throttle position changed slightly from fast idle to warm-up, so you can see very little throttle to increase the rpms.... could be a slightly dead spot in the TPS, it will test good but can be iffy. At this point, a slight change in TPS position could keep you off that wee dead spot.
Busy morning but later today, I'll dig up a more accurate test method by back-probing the TPS with a VOM. Also there is a thread where I dissected a TPS to see how it is contructed.
 

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Discussion Starter #15 (Edited)
Throttle position changed slightly from fast idle to warm-up, so you can see very little throttle to increase the rpms.... could be a slightly dead spot in the TPS, it will test good but can be iffy. At this point, a slight change in TPS position could keep you off that wee dead spot.
Busy morning but later today, I'll dig up a more accurate test method by back-probing the TPS with a VOM. Also there is a thread where I dissected a TPS to see how it is contructed.
I turned TPS clockwise , it now shows 11.7% on idle and it starts straight away...

I also checked voltage st different points and it consistently shows 12.7V when ignition off and 13.9-14.1V when on idle. This sounds okay to me

 

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Pics in this thread
https://www.fjrowners.com/forums/9-fjr-technical/148517-tps-question.html

From another sandbox, my buddy Alan....
Quoting ionbeam's instructions.....
"... there is no need to guess about the TPS. Back-probe the TPS connector. Black DMM lead on the Black/Blue wire and the red DMM lead on the Yellow signal wire. At idle read .63 to .73 volts. Don't sweat a few milli-volts if it out of range. The way the TPS is attached to the main throttle body shaft the TPS idle voltage reading will change if you adjust the idle speed using the manual adjuster on the right side frame area. The ECU is mostly looking at throttle rate of change and span of throttle change instead of absolute voltage. If the TPS is bad in a narrow portion of the resistive track the ECU will see the sudden drop as a fast throttle change and will chop the FI off via the decel fuel cutoff and then when past the resistive track defect the ECU will see the sudden voltage rise like the rider is pinning the throttle wide open for a brief second and it's this rapid off/on that the ECU sees that makes the engine run so rough or outright stall.

Leave the meter back-probed to the TPS, Velcro/rubber band the meter to your handlebars and for a ride until it heats up. When the off idle misfire happens watch the meter. If it's the TPS, the voltage on the meter will notch down dramatically then come back up as you get the throttle beyond the (potentially) damaged spot inside the TPS. Steady, linear voltage = good TPS = look elsewhere.

The ECU provides +5 volt reference to most sensors and uses an isolated ground from the ECU so it is best to ground the meter to the Black/Blue wire and not chassis or battery ground."
 
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Thanks for posting the details on your diagnosis procedures. Unusual to find a problem that hasn’t been encountered/resolved by others on this board. Sorry to hear about your problem- I know how frustrating it can be. My TPS went bad at low miles but the problem was in the 3,500 RPM range which is where it spends a lot of time on the road. Haven’t heard of one failing in the idle range but anything is possible. Wish I had more to offer. Best of luck getting it resolved - sounds like you are taking a very meticulous approach to trying to diagnose it properly. I hate to just throw parts at problems in the hope that it will fix it. Please keep us posted on the fix - info like this is the real power of these forums. I for one am following this thread with interest.
 

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Go with the Seafoam at 1 ounce per gallon. Overtime, this new ethanol gas we are using is causing problems. I had same issues earlier and the guys gave me a lot of info also but try the seafoam.
 

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Discussion Starter #19 (Edited)
Sorry for going quiet. Busy at work but will carry on mid week.

I'm very suspicious re TPS. As you said it would make sense to be worn at certain RPM not idle. This is very bizarre. Bike was ridden mainly with CC set on 70mph so unless this corsponds with the same position of TB as on idle.

I have ordered seafoam however I'm sceptical,) there must be an issue. I'm not going to buy random parts, def prefer to diagnose it properly.

As I said previously all I did for now is I rotated TPS clockwise by a touch. Bike starts warm without any issues, idle is around 1060rpm and stable, TPS reads 11.7% vs 14.8% when bike was stalling
 

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Sometimes the best you can do is take an educated guess especially when one of the parts in question doesn’t always test bad when in fact it is. The good news is that a new TPS is only around $120 so not a super expensive guess. If you do go this route, do yourself a favor and replace those security torx screws with allen head screws so you can use an Allen key to easily get it out if it should ever go bad again in the future. I have no confidence that Yamaha has addressed this issue with the manufacturer of the TPS.
 
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