Strange idle, Gen 1

[Queensland Ken]

Hi,

Been working on a mates Gen 1 today. It's actually a 05 Gen 1 USA import to Australia.

He told me of a really weird idle issue when he arrived.

Being a Gen 2 rider, I thought I'd ask the question.

When the bike starts, cold idle is up to 2000 rpm.

When in gear, it then increases up to 3500 rpm for up to 10 kms, then slowly decreases to a normal idle rpm of about 1100 rpm.

After doing his suspension linkages and drive, we started the bike, yep, cold idle 2K rpms.

Nick it into 1st while on the centre stand, and straight away increases to 3.5 K rpms, knock it out of gear the idle settles back to 2K rpms.

He said it takes awhile to reach normal idle revs, about 10 Kms

Was at about 2 bars on the temp gauge.

No fault codes.

Dash code indicated 89 degree coolant temp.

I take it a Gen 1 has a different cold / hot idle system to a Gen 2. ?

Looks like the cold idle speed is driven by the ECU via the temp sensor off the end of the coolant "pipe 1" (ref: part 24 on the parts lookup)

Some info on page 1-23 on the service manual.

Could the strange idle be caused by an air lock / bubble down along that coolant pipe ???

 

[TomInPA]

Your answer is available by entering a google search: fast idle site:fjrforum.com

https://www.fjrforum.com/forum/index.php?showtopic=122016

Not much I can add to what has already been said and the fix is not too difficult.

 

[Graham Downunder]

Ken it sounds really funny that it increases so much when in gear??? . Before going too far if this bike has done this for a while I would, when warm, set the idle at 1100 rpm add some Nulon Injector cleaner at double strength in the bike with some ordinary fuel from a busy petrol station,run a full tank before trying to fix a problem that may go away . Not on FJRs ,but on some other bikes in Australia I have heard of people that have picked up bad fuel that has caused some funny problems including too fast idle that has been cured this way . Has the coolant been replaced recently ?? as it may have a big airlock in it .

 

[Queensland Ken]

We did a service to the bike some months ago and burped the system several times, even the day he took off back to Brissy.

That's what I can't find, the increase in revs when in gear, spent a few hours Google searching all the forums on this particular fault.

I had a blockage on Goldie's coolant tubes that affected the hot / cold idle system, the "wax" fuse, after a valve check.

This symptom is different to what I experienced, my bike was stalling out, Klem's bike is increasing revs, to 3500 rpm.

In gear 3500 rpm, neutral 2000 rpm, in gear 3500 rpm, neutral 2000rpm etc etc

It finally drops to a normal idle after a long period of time.

Been doing a bit of light reading on the Gen 1 and Gen 2 manuals.

It does seem that the coolant sensor plays a big part in "the enrichment" of the A:F ratio on warm up.

The coolant wiring diagram shows a direct input into the ECU.

I'm thinking that there is an air lock in that coolant pipe, part # 13 on page 6-6 (gen 2), that's affecting cold idle in a different manner.

Either way the system has to be bleed out fully again.

Klem is up again next week, I did mention it to him this arvo to burp it a few more times.

After-start enrichment
After-start enrichment provides enrichment compensation during a prescribed duration following the starting (firing) of the engine.While the amount of fuel enrichment is determined by the after-start enrichment coefficient, the coefficient varies by the coolant temperature.

Although the coolant temperature determines the initial starting enrichment coefficient, the coefficient subsequently changes in accordance with the damping factor.

The enrichment ratio is the highest immediately after the engine is started, and diminishes gradually.

The enrichment of fuel in this manner ensures a stable engine operation immediately after the engine is started.

Warm-up enrichment
When the coolant temperature is low, a warm-up coefficient is applied in accordance with the signals from the coolant temperature sensor in order to effect fuel enrichment.

Because the coolant temperature determines the coefficient, the coefficient changes with the fluctuations in the coolant temperature.

The coefficient increases with the decrease in the coolant temperature, and decreases with the increase in the coolant temperature.

The ratio of fuel enrichment also changes with the changes in the coefficient.

 

[wfooshee]

The ECU has no control over the throttle, even for cold idle. It only has control of the air/fuel ratio.

Cold idle is controlled by a melting-wax device under the throttle bodies, through which engine coolant flows. More details than you could ever have imagined here.

Changing when in gear is the big mystery to me. I don't know of any "in gear" input to the ECU except that it has a line on the neutral/clutch input to the starter interlock. While fast idling in gear, does it slow down with the clutch pulled like it would if you shifted to neutral? If so, that would indicate ECU meddling. If not, then not.

One wonders if the O2 sensor is disconnected. That's the only monitor the ECU has for air/fuel ratio, and if disconnected, it falls back onto a best guess strategy. Disconnected O2 is common on Power Commander equipped bikes. If there's a Power Commander, maybe loading an all-zeroes map and reconnecting the O2 sensor might tell us something.....

 

[ionbeam]

Even if the 'wax motor' thinks the engine is cold the idle shouldn't go up that high. There may be more to this story.

Does the bike have a throttle lock?

Does the idle change when the handlebars are turned from lock to lock?

A vacuum leak can cause a high and wandering idle but also would come with driveability issues.

Is there a true cruse control installed? The throttle connection linkage could cause the throttle to stick.

Has someone done the spring unwind? Could cause the throttle to stick. When the handlebar throttle is released does the throttle tab on the cam return to the stop on the throttle bodies?

When the idle is high is the throttle tab on the stop?

Off the wall, how much play is there in the throttle cable?

 

[BikerGeek99]

Would a wacky TPS have any impact here?

 

[ionbeam]

Would a wacky TPS have any impact here?

Good thought but the TPS couldn't cause these symptoms without causing some serious driveability problems.

 

[Queensland Ken]

Unfortunately the bike is in Brisbane and I'm in Toowoomba.

I know of RadioHowie's great post on the system, got me out of a pickle once when I had problems.

TPS indicates fine, 15-99.

The bike has a throttle lock, good free play.

Don't know about a unwound throttle spring.

No increase in rpm's with handlebars turned from lock to lock.

I think there was still high revs with the clutch pulled in, running in gear. Will have to check again and note that.

We did adjust up the slack in the throttle cable 2 months ago, there is still too much play. He wanted me to take a bit more out yesterday, I didn't.

Has a PC3 BUT it's been disconnected, I take it the O2 sensor has been disconnected, may not have been reinstalled.

No wandering idle, I had a cracked vacuum cap once, and a incorrectly installed MCC cruise control on my bike, know that symptom.

I just can't understand why the revs increase to 3500 each time the bike is in gear, running on the centre stand.

The ECU is doing something there.

We changed out the plugs, did a TBS, oils and air cleaner, and changed out the coolant.

One throttle body is just about out of adjustment, maybe due for an unauthorised TBS. But all were relatively equal.

We burped out the system quite a few times.

I'll just have to go through and check everything when he comes up next week.

 

[RadioHowie]

Having had "some" input in the thread wfooshee linked to, and being in possession of the finest running FJR in the entire universe, I can't think of any connection between the transmission being in gear and the idle increasing. There's really just no connection between the two.

While the ECU may be aware of the difference between "in gear" and "in neutral", it can't crack the throttle open, and there is NO connection between the ECU and the fast-idle mechanism, which is purely mechanical, based on coolant temperature. If it's cold, the idle is raised by air-bleed valves being opened in the throttle bodies. As the mechanism is heated, the air-bleed valves close, reducing the idle speed to normal.

Even if the ECU would somehow increase the richness of the mixture while in gear, and then lower the mixture ratio while in neutral, that wouldn't really raise the idle speed. That is strictly a product of increased air coming through the throttle bodies, hence the necessity of the fast idle mechanism.

Personally, thinking about the problem as has been described, I'm stumped.

 

[Queensland Ken]

Just had a call from a mate in Sydney who described a very similar fault with his previous FJR.

His bike became un-rideable and too dangerous, revs going up to 3500 rpm at any time.

His mechanic he uses is Yamaha trained, knows the FJR and now has his own business.

(The mechanic did my first valve check on my 06, rode to Sydney because he is trusted).

They ended up removing the spring / disconnecting the cold idle from the bike.

He then used to bring the bike up to temp just using his throttle lock.

If all else fails next week, we may just end up disconnecting it, see what happens.

I'll try to take a video of the symptoms before I touch the bike.

 

[Donal]

Having had "some" input in the thread wfooshee linked to, and being in possession of the finest running FJR in the entire universe, I can't think of any connection between the transmission being in gear and the idle increasing. There's really just no connection between the two.
While the ECU may be aware of the difference between "in gear" and "in neutral", it can't crack the throttle open, and there is NO connection between the ECU and the fast-idle mechanism, which is purely mechanical, based on coolant temperature. If it's cold, the idle is raised by air-bleed valves being opened in the throttle bodies. As the mechanism is heated, the air-bleed valves close, reducing the idle speed to normal.

Even if the ECU would somehow increase the richness of the mixture while in gear, and then lower the mixture ratio while in neutral, that wouldn't really raise the idle speed. That is strictly a product of increased air coming through the throttle bodies, hence the necessity of the fast idle mechanism.

Personally, thinking about the problem as has been described, I'm stumped.

I think this puts it all in context. Before you go removing anything or carrying out any major surgery I would set the bike up so you can run it with the tank off. I do this by placing the tank on a stand on the left hand side, the fuel line and pump supply will reach on that that side (if you get the height right).

Then carefully observe the throttles as you put the bike in gear. It sounds like there is some sort of mechanical 'linkage' going on. As Howie said above there is no known way for the ECU to alter the throttles.

Watching this one with interest.........................

 

[Queensland Ken]

Watching this one with interest.........................

So am I, lol lol.

Not going to do any surgery just yet and I really want to take a video of it happening.

The gent may come on up this Sunday and to top it off, it's only a cold idle "thing" so we can only check it each time it cools down.

I know that there is no connection between the ECU and the throttle bodies.

But something is happening to cause the higher revs only when in gear and not to settle down until the bike is well and truly warm.

Maybe a stuck fast idle valve or valves, or a linkage come off under the TB's somewhere ????

I've tried heaps of different google search terms on most FJR forums.

And luck has it, another FJR owner who lives nearby and willing to help out.

Got me bloody stumped.

 

[RaYzerman19]

You mention one TBS screw is almost out of adjustment. I would redo the TBS, ensuring that you start with #3 screw out one full turn. It still may not cure your issue, but at least you shouldn't run out of adjustment.... when you do, it is hard to get a proper idle speed.

 

[Queensland Ken]

Well my mate came up to Toowoomba today and had no success.

Really gave the coolant system a good "burp" and a heap of small air bubbles came up and a few big burps.

Thought I'd had it, bummer.

Had to keep hosing down the bike to cool it off so we could trace things out.

Starting to think it's something to do with the fast idle valves as in RadioHowie's posts, all gummed up.

I'm going to do surgery and remove the spring.

Below is a Utube of the bike started up with higher than normal revs, then up to 3000rpm while in gear.

The revs decease every time the clutch is pulled in and will eventual return to a normal 1000rpm at about 3 bars indicated.

[YouTube]

[/YouTube]

 

[RadioHowie]

Okay, after watching the video, the issue has been clarified, somewhat....

I was under the impression the idle speed increased simply by clicking the bike into gear. That obviously is NOT the problem. You apparently have the bike on the centerstand, as I can definitely see the speedometer increase with the tachometer increase. So, as the clutch is released, the transmission engages, spins the back wheel, and up goes the rpm.

At least now I know that the issue isn't what I originally thought, that the simple act of clicking into gear was raising the idle speed, but I still don't have a freakin' clue why the engine speed would increase by running the bike with the transmission in gear and the rear wheel free-wheeling.

It's possessed!!!

Also, I can definitively say that with 2 bars showing on the temp gauge, 1700 rpm idles is WAY too high! Methinks there's something screwy with the idle adjustment and/or the throttle body linkage or synch settings.

 

[ionbeam]

I think dcarver 'discovered' this 'problem' a few years ago and documented it with a video too. Dunno if Don can remember this far back

 

[Queensland Ken]

Just tried to search dcarver's posts, the board will only let me "Search limited from 27-July 12", bugger.

Will do a few Google searches latter on today, nice weather here so off on the bike..

I keep telling him he should have bought my 06 instead.

 

[Queensland Ken]

Hi,

Success.

Today we gained access to the side of the throttle bodies and with the help of a rather crappy USB camera for a lap top, diagnosed the problem.

Looks like someone prior had wound the fast idle adjustment screw all the way in. WHY ??

The bike was still warm / hot when we lifted the tank and noted that the plunger of the wax fuse was fully extended out and that the fast idle valves were still opened.

The plunger pushes a rail that operates when up to temp and closes off the fast idle valves.

When the engine was still hot, backed off the adjustment screw until the valves were seated into the throttle bodies.

Can only see 1 valve as such on the LHS of the bike. The USB camera was rather useless on the other valves.

Cooled the bike off twice and adjusted the cold idle up twice, it's going to be hit and miss as there seems to be a "sweet spot " on the adjustment range.

It did change the hot idle settings and nipped that up a bit as well, a real bugger seeing it's a cold engine "thing"

At least the bike isn't revving to 3500 rpm's or stalling out and the hot idle is coming on around 1 bar.

Still need to tweak up the cold idle revs a bit more.

Really don't know why the bike showed all the other weird symptoms, up to 3500 rpm's when in gear, 2000 rpm when in neutral or when the clutch is pulled in.

Must be various inputs into the ECU that effects injector duration.

The only explanation I can think of is the previous owner did a coolant change, had an air lock in the coolant tubes for the cold idle circuit, kept stalling out the bike when cold and masked the fault by bumping up the cold idle setting.

Thanks RadioHowie for the write up