3rd Gen Idle speed problems

[Fred W]

In the past few months I’ve been experiencing two possibly related idle speed problems.
 

 The first one has been going on longer, which is why they may not be related.  When I cold start the bike it often fires one or two cylinders when you would expect, and then stalls out.  I’ve learned to hold the starter button down longer and it will usually complete the starting after one or more skipped cylinders (misfire). Once I get the bike running the cold idle speed is only about 1500 rpm, which seems a bit low to me.  I compared mine to Big Ogre’s 2015 and his cold idle is considerably higher, but he’s had the Ivan ECU flash upgrade installed, which might affect idle speed.

Second weirdness is that after starting and riding off, when later coming to a stop sign, pull in the clutch and the idle speed hangs high at 2000 to 2500 rpm.  It doesn’t cause any problem when riding except a small loss of engine braking.  After riding for 20-30 minutes the problem goes away and idle returns to the normal 1000-1100 rpm.  Someone else noted a similar situation on another thread that I couldn’t find again.

 I’ve done a valve check since both of these things started occurring (all in spec) and that service included installing new spark plugs.  Haven’t had the brake lever switch recall done yet, but don’t see how that would be related, and it appears to be working ok (brake lights and cruise control now working fine)

I haven’t dug into how the 3rd Gen idle speed is controlled yet in the FSM, but will do that in the next few days as I’m recovering from my second hip replacement and have some down time just before winter.  
 

Just wondering how common these symptoms are for other 2013-2015 FJR owners as we share similar configurations.

 

[RossKean]

Throttle position sensor???

Was also thinking O2 sensor but I think you would see issues with funky mixture and poor mileage,

 

[escapefjrtist]

Ivan's flash does increase the cold start idle to ~2000-2100 rpm. Before the flash and IIRC, my '15 was ~1400-1500 rpm on cold start. My '15 has never had issues dropping cylinders on start-up except in one instance. Similar to what you've described Fred, difficulty starting, missing and just odd behavior. Hot starts were fine. After checking everything obvious, finally traced it to bad fuel. The bike sat for 4 - 5 weeks with a full tank...(MBD). Once I burned enough of the tank, topped off with new and the issues disappeared. With the fresh tank I immediately felt improved running. YMMV

~G

 

[Fred W]

Throttle position sensor???

Was also thinking O2 sensor but I think you would see issues with funky mixture and poor mileage,

A potential sensor problem has been in the back of my mind.  Because of the fly-by-wire there are two position throttle sensors that could mess up.  One on the throttle plates (traditional TPS) and one on the end of the cables going to the twist grip sending the twist grip position.  Was also thinking maybe a flaky temp sensor could cause both symptoms.

I believe the O2 sensor doesn’t come into play until everything is up to operating temps.

 

[Fred W]

Ivan's flash does increase the cold start idle to ~2000-2100 rpm. Before the flash and IIRC, my '15 was ~1400-1500 rpm on cold start. My '15 has never had issues dropping cylinders on start-up except in one instance. Similar to what you've described Fred, difficulty starting, missing and just odd behavior. Hot starts were fine. After checking everything obvious, finally traced it to bad fuel. The bike sat for 4 - 5 weeks with a full tank...(MBD). Once I burned enough of the tank, topped off with new and the issues disappeared. With the fresh tank I immediately felt improved running. YMMV

~G

Bad fuel is something I hadn’t really considered.  I am definitely not riding the FJR as often as I once was, with a couple other choices in the garage.  Of course that would only explain the hard start symptom and not the hanging idle, but it is very possible they are unrelated.  Thanks for the confirmation that the flash raises the idle speed.  

 

[RossKean]

A potential sensor problem has been in the back of my mind.

There has certainly been some history of TPS issues in early Gen IIIs.  Hard to prove without a replacement.  Unfortunately, looking at output as a function of throttle position in your garage may not simulate real world function as I am sure you know.

Haven't heard of a temperature sensor failure but it could certainly mess things up.

As for the hanging high idle, any chance that you have insufficient slack in the throttle cable so it isn't always returning to zero?  A little more freeplay and/or a drop of lube might help...

 

[Fred W]

Yeah, my friend Big Ogre got bitten by a bad TPS, but his symptoms were more typical TPS symptoms of stumbling at throttle roll-on or off.  I know that is always a possibility on any fuel injected bike.  
 

Hanging idle definitely isn’t cables.  When it happens I’ve tried forcefully closing the throttle to no avail.  It could be something fetching up on the other side of the fly-by-wire servo system (servo motor driving the throttle plates) or something electrical in that system.

 

[roger dodger]

My 2013 was exhibiting 'smoothness issues' and I ignored it as along as possible.  Then I did the TPS replacement (with help from NBB) .

My buddies 2014 was exhibiting big shifting smooth 'issues' and he fought with it. We did the TPS together and his first response was ' I got a new bike again!!!'

For $100 or so for a new part, I would suggest a new TPS and follow the detailed instructions on the tech page.  It may solve your problem instantly.   Or it may rule out the TPS entirely.  But you'll be done wondering ...      YMMV

 

[mcatrophy]

Haven't heard of a temperature sensor failure but it could certainly mess things up.

If that was the problem, you could check by looking at the coolant temperature "C.TEMP" on the display. When the engine is cold this displays "Lo", if it shows any digits then the ECU will think the engine is warm.

 

[RossKean]

If that was the problem, you could check by looking at the coolant temperature "C.TEMP" on the display. When the engine is cold this displays "Lo", if it shows any digits then the ECU will think the engine is warm.

I was thinking more about intake air temperature rather than coolant.  The ambient air temperature is not the same sensor as intake air temperature - at least it isn't on a Gen II.  I wonder what effect an incorrect intake temperature would have...?

 

[mcatrophy]

I was thinking more about intake air temperature rather than coolant.  The ambient air temperature is not the same sensor as intake air temperature - at least it isn't on a Gen II.

I would have thought cold idle is required because the engine is cold rather than the ambient air is cold. The latter is more for fine control of mixture to achieve low emissions, this wouldn't affect the requirement for fast idle when the engine is first started.

The Gen 3 idle, hot and cold, is controlled directly by the ECU adjusting the throttle, rather than the hot wax mechanical gismo used by the Gen 2. Coolant temperature is the obvious place to check for engine temperature.

 

[Fred W]

I took the time to dig through the 2014 FSM today.  Information about idle speed control (either cold or normal) is very scarce. There is a brief mention in the fuel injection theory about it being simplified (no bypass or valve) but nothing more.  There is also a diagnostic that will allow you to reset the learned idle speed.  Seems simple enough to do.  
 

Anyone ever tried it?  What results did you get?

 

[Fingloid]

I tried resetring and it messed up big time. Can relearn the idle again. Now, i dont have idle