Further details on Fast Idle system

[RadioHowie]

There's been a lot of discussion about fast idles on FJRs the past few months, many of which I've participated in.

I've just finished removal of my 04's throttle bodies and disassembly of the fast idle mechanism to possibly clarify some issues that may be present.

Here's the throttle bodies removed from the intake spigots, viewed from the motor side of the TBs. The Fast idle mechanism is clearly visible along with the two coolant hoses that run to the "wax motor" that controls movement of the assembly. For those just joining in on the discussion, when the motor is cold, there is a wax plug in the cylindrical area of the "wax motor" between what I've labeled "Fast Idle Adust" and "Coolant hoses." When the unit is cold and the wax has solidified, the entire assembly slides to the right (in this picture) pulling the fast idle valves OUT of the throttle bodies, allowing more air into the intake, effectively increasing the idle speed. It has been reported that Gen I motors' fast idles are in the 2000-2100rpm range, while Gen IIs typically run around 1500rpm. It is also speculated that 1500rpm may be too low, causing misfiring and "clunking" of Gen II motors when cold started.

Here is a close-up of the adjusting screw on the fast idle mechanism.

Closeups of two of the four fast idle valves mounted in the bottom of the throttle bodies.

As the motor warms up, hot coolant from the motor flows through the wax motor, melting the wax plug, and as the wax melts, it also expands with heat, forcing the entire fast idle assembly to slide to the left, allowing springs in the fast idle valves to seat, closing off the bypass ports which allow fast idle, thereby returning the idle to normal, which should be set statically at 1100rpm.

As noted above, may Gen IIs have been reported with fast idles of only 1500rpm, which may be too low for a consistent cold idle. In this picture, a close-up of the actual adjusting mechanism, you can see that the distance from the left of the adjusting screw bracket, A & B, to the side of the bracket that contacts the wax motor "piston", D is static in distance, but the adjusting screw contacts a second, spring loaded bracket at C, which is part of the sliding assembly that pulls the fast idle valves out to increase the idle speed. So screwing IN the fast idle adjusting screw moves the entire valve assembly to the right, increasing the fast idle speed by pulling the fast idle valves out further when cold.

As the motor warms, the wax plug melts, the liquid wax expands and pushes the entire fast idle assembly to the left (again in orientation with these pictures) and compression springs in the fast idle valves cause the valves to retract back into the throttle bodies, closing off the bypass ports, and reducing the idle to "normal".

Here is TB #1 with the fast idle valve removed.

And here's a problem I found with my fast idle valves. This is a closeup of the valve from TB#1, by the rider's left knee.

All four were seriously gunked up with crud, so when the motor warms and the fast idle mechanism retracts, the valves are very hesitant to seat, i.e., return to "normal" idle position. Unfortunately, the valves are longer than the clearance between the throttle body castings, and therefore it's impossible to completely remove the fast idle valves from TBs #2, 3 & 4 without separating the TBs, a process I don't recommend. You can, though, loosen them from the TB castings with a 12mm wrench, pull them out about 75% of the way and soak the bores with suitable cleaner, manually work the valves in and out to clean out the bores.

My 04 has 46,000 miles on it and you can see the amount of crud on that one valve. All 4 are that dirty, so I would recommend TB removal and fast idle valve cleaning be added to your FJR's maintenance schedule at some point in its lifespan.

'Howie

Edit: BTW, don't know if increasing the fast idle to ~ 2k rpm is a good idea for AE models. Will the bike atttempt to engage the clutch if the bike's in gear at this rpm???

 

[FJRay]

Do you have ethanol shit fuel where you are??? I seem to see a lot more build up in fuel systems in my shop than I did before the shit gas. Just wondering if it makes a diff. I have one station close to me that has straight gas for boats and off road. I don't know that it helps but it makes me happy.

 

[RadioHowie]

Do you have ethanol shit fuel where you are??? I seem to see a lot more build up in fuel systems in my shop than I did before the shit gas. Just wondering if it makes a diff. I have one station close to me that has straight gas for boats and off road. I don't know that it helps but it makes me happy.

Oh yeah....at least 10% ethanol everywhere I buy gas.

Don't know for sure if that's the problem, but the intake is tract is just a mess.

All 4 throttle bodies, airbox side and cylinder head side, are just filthy, as are the intake ports themselves.

All 4 look the same. The injectors are on the cylinder head side of the throttle plates, so all the SeaFoam and Techron in the world aren't gonna keep the airbox side of the throttle bodies clean. I've never run anything but Chevron gas, with Techron, in this bike for the last 30,00+ miles (since I bought it), so all that crap is with a Tier 1 gasoline brand run through it.

It's not just a shame.....it's downright disgusting. Can't be good for the motor. I can't wait to get the motor out of the frame so i can finish pulling of the cylinder head and get some pictures of the combustion chambers.

Since the throttle bodies are basically just machined "holes", without floats or such like carbs, I'm tempted to take them to a shop and have them "boiled" out, or whatever it is shops do to clean intake systems.

Right now, since I've kept clean air filters in the Feej from the day I bought it, I was convinced all the crud is hydrocarbon build-up from the crankcase ventilation system, which is plumbed into the airbox.

BUT, before blaming the PCV system, I thought I'd dissect the airbox for further study.

I expected the inside of the airbox to be a gummy, oily mess from crankcase ventilation.

I was wrong. Ater opening the airbox, I was surprised how clean the inside actually is. No puddles of oil, or thick films of "goo".

The air filter is clean. The intake tubes are clean. The area around the "T", which is the back side of the PCV inlet, is clean.

In fact, everything is surprisingly clean. The filtration system is doing an excellent job, IMHO.

So where is all the crap in the intake tract coming from?

I'm beginning to suspect combustion blowback. All the crap on the airbox side of the butterflies can't be from gas, since the injectors are downstream from the butterflies.

So where is all the gunk coming from? Unless that's normal for 46k miles?????

'Howie

 

[Constant Mesh]

I wouldn't perform any maintenance on the fast idle system until TB syncing identified a valve not completely closing.

If you connect your syncing equipment onto the TB's before a cold startup you can watch the individual vacuums increase as the coolant warms and the fast idle valves close.

 

[RadioHowie]

I wouldn't perform any maintenance on the fast idle system until TB syncing identified a valve not completely closing.
If you connect your syncing equipment onto the TB's before a cold startup you can watch the individual vacuums increase as the coolant warms and the fast idle valves close.

True, but a visual inspection could be carried out as well, forcing the sliding rail, accessed at the left end of the TB assembly, to the right, allowing the fast idle valves to then close on their own. They are visible from above and one could see if they're closing on their own.

Perhaps sticky valves are the reasons some folks NEVER see decent vacuum levels when attempting TB syncs.

You read it here all the time..."I can't get my carbtune to ready anwhere close to 250mm/hg"...may be sticking valves.

'Howie

 

[chrisflock]

I'm not sure about the buildup on your throttle bodies, I think part of the issue with the buildup is that it preferentially sticks to different materials (some of it may be materials, and some may be temperature?)

Here's some examples:

98 Neon SOHC (donor vehicle), over a 100k miles, intake tracts in head were very dirty, PLASTIC intake manifold clean, aluminum throttle body housing and throttle body pretty dirty...

98 neon DOHC (transplant recipient), over 100k miles, intake tracts in headfairly dirty, aluminum intake fairly dirty, aluminum throttle body housing not very dirty...PCV system was running a breather instead of running to intake for at least 30k miles (aftermarket cold-air intake)

76 Small block chevy, PCV vented with breathers for as long as I know, intake, heads, and carb throttles were pretty darn clean (small buildup in the intake under the center of the 4 throttles) some crud on the rougher portions of intake tracts

84 Small Block Crate (stuffed into early 80's, carb van), complete emissions system intact, intake (aluminum) had thick coating of crud to the point you could scoop it out of the intake manifold with your fingers, head (cast iron) had a significant buildup of crud, but it wasn't as gooey as what was on the intake.

Corvair (60, 61, 62, I'm not sure, the engine had no car holding it back) intakes and heads very clean, as I understand there was emissions system to speak of for this car.

Of course, there are many variables that aren't, and cant', be addressed, this is just some guy's experience.

 

[DailyCommuter]

Perhaps sticky valves are the reasons some folks NEVER see decent vacuum levels when attempting TB syncs.
You read it here all the time..."I can't get my carbtune to ready anwhere close to 250mm/hg"...may be sticking valves.

'Howie

I had that same problem just the other day, couldn't get more than 220mm/hg and my idle (on a fully warmed up engine) couldn't be raised up above 1000 rpm... the adjuster knob was all the way in no room left to turn, on BrkK12's advice, I backed out the air screws on the individual tb's (the one's used to perform a sync) to 1 1/4 turns out, and turned the idle adjuster out 3 full turns. The adjustment of the air screws gave my back my idle adjustment, and when I performed the sync. at 1150-1200 rpm (approx). I wa able to get 250mm/hg out of them all. fwiw I think anyone having the low vacuum read issue when doing a TBS should try that. I was all set to start some major work, before Dan saved me the headache by suggesting that. I thought I would have to adjust the butterfly stop screws to get the idle up, and then back off the idle adjuster knob, to get the adjustability back. What I learned during this little job, was that my assumption that the idle adjustment screw on the FJR was a mechanical type screw/stop like you would see on a lawn mower or other small engine, when it is in fact an Master air screw for all 4 of the throttle bodies. so if the individual ones are to far in, then the master one willnot be able to adjust the mixture enough to get the idle up. Dab pointed out to me that chasing that 250mm number in the first place was what got me into trouble, all my four air screws were very close to all the way in to start with.

 

[Constant Mesh]

If you don't adjust the TB3 air screw (i.e., keep the factory setting) as the manual recommends then you won't have the idle adjustment problem.

You also don't want to be screwing around with the individual throttle valve closed position limiters. There's no good reason to touch those.

On the '06 and later models the throttle valve closed position isn't adjusted for idle rpm control. The throttle cam tang comes to rest on a fixed height peg. So the closed position is fixed -- not adjustable.

Too much adjusting going on!

 

[DailyCommuter]

Believe me I know I don't want to screw with those. I was looking for any reason not to. Which fortunately Dan gave me before I did. But answer me this... If the fsm says 250mm/hg is what you want... And #3 is at 220 mm/hg, then how do you go about doing a TBS, and bringing them to all be even at 250 if the one your matching the other 3 to isn't where it is supposed to be to begin with....

 

[FJRBluesman]

Howie thanks! Your A, B, C, D, photo and verbiage answered the $64K question, which way to turn the adjust screw.

I can't believe how dirty your TB's are. They should be fairly clean. Just think of all the crap your motor injests that doesn't stick to the air filter or TB's.

Excellent break down and explanation.

 

[wfooshee]

Just a note about the throttle bodies and crud on the plates. The lack of such gunk upstream in the breather system may or may not mean anything. None of it means much to me. I was just thinking and comparing to automotive systems, and in a car, you have the throttle at the beginning of an air intake plenum, and PCV goes into that plenum, behind the throttle. In our engine, the throttle is the last thing any air or other molecule sees before it goes past the injector into the intake valve, and there's no space in that short distance to handle crankcase ventilation, so it dumps into the airbox.

Mine didn't look that bad first time I took the throttle bodies off last spring, and after cleaning them they were still pretty clean a couple weeks ago with the starter issues. But on mine the crud was just on the plates. I had none on the aluminum throats of the throttle bodies, it seemed to condense and collect just on the throttle plates. Similar to yours, nothing at all in the airbox itself.

Don't know that it means anything, just a comparitive observation.

 

[RadioHowie]

Shee-it, man......what the hell you doin' up this hour?

Only reason I'M up is a call from the office with computer problems I had to fix over the Neenernet with Remote Desktop.

Of course, I HAD to check my email to see what foolish Feejers were reading posts this time of night morning.

GO TO BED!!! I am.

 

[Bogus]

I was beginning to wonder if you were retired or independantly wealthy Howie! How the hell do you find the time to work, disassemble/assemble your Feej, and still manage to take pictures and share the journey with us in such detail?? Kudos to you man :yahoo:

By the way, I'm up at this ungodly hour because I'm on the night shift this weekend :angry:

 

[Fred W]

Howie,

Thanks for filling in the holes in our fast idle mechanism knowledge. Ever since we had that discussion about there even being a fast idle mechanism I have wondered if the thing is adjustable.

The idea of sticky fast idle pistons is an interesting one. The wax motor forces them all open, but the little spring around each piston is responsible for them closing. Too bad it is such a royal PITA to get at them for cleaning. Makes doing a valve check/adjust look like a walk in the park.

As to the gunky buildup, it sure does seem excessive to me, especially considering the relatively low mileage. To be honest, I would be happier knowing it was blow back from the engine or the PCV venting spooge. At least the stuff would have come from inside the engine and not be as likely to cause increases in wear. If this is something else getting past the air filter, well all bets are off.

You point out that the PCV connection in the airbox is clean looking, what about the PAIR connection port? When I pulled the PAIR stuff off and replaced with the WynnPro covers there was a similar looking spooge all over the intake side of the reed valves. If the reeds do any leaking it would be possible to get exhaust flow back into the intake when the PAIR valve is open, no?

 

[HaulinAshe]

(...)You point out that the PCV connection in the airbox is clean looking, what about the PAIR connection port? When I pulled the PAIR stuff off and replaced with the WynnPro covers there was a similar looking spooge all over the intake side of the reed valves. If the reeds do any leaking it would be possible to get exhaust flow back into the intake when the PAIR valve is open, no?

Ding, ding, ding!

IMO we have a winner. Fred is right-on.

My latest experience with the PAIR system at 75,000 miles, has me suspecting it for all sorts of problems. There's absolutely no doubt that my PAIR system was backwashing into the intake. The reeds were badly carboned and when I did the simple capping of hoses on the PAIR, within a couple weeks some hoses collapsed while some remained intact. It was not a pretty sight.

Gentlemen, a set of PAIR system cover plates and a generous supply of Sea Foam has become part of every FJR's future that I service.

Oh, and thanks Howie! It's great of you to stay up late taking pictures and diagraming all that stuff we can't easily reach.

 

[wfooshee]

Shee-it, man......what the hell you doin' up this hour?
Only reason I'M up is a call from the office with computer problems I had to fix over the Neenernet with Remote Desktop.

Of course, I HAD to check my email to see what foolish Feejers were reading posts this time of night morning.

GO TO BED!!! I am.

I'm in Central time, wasn't that late!

But I did retire immediately after that forum session.

 

[RadioHowie]

I was beginning to wonder if you were retired or independantly wealthy Howie!

BWAH!!! "Independently wealthy" Now THAT'S a good one! I wouldn't even be working on the Feej if it hadn't been for the incredible generosity of the forum. If it hadn't been for this bunch of dinks, the bike would have been sold.

Oh.....too broke to retire.

How the hell do you find the time to work, disassemble/assemble your Feej, and still manage to take pictures and share the journey with us in such detail??

Well, the a week IS 168 hours long, so subtracting work & sleep hours, that leaves me about 38 hours a week to work on the bike. But if you count time I spend on the forum, I'm pretty much in the hole, time wise.

Plus, I keep the camera right next to me while I work, taking pictures of stuff so I'll have a reference when it all goes back together. MissusHowie is pissed about the grease on the camera body, though. <_< I just tell her "Get back in the kitchen, bitch!"

 

[RadioHowie]

Oh, and thanks Howie! It's great of you to stay up late taking pictures and diagraming all that stuff we can't easily reach.

Easy fix for that.....take out your CCT and crank up the motor!

You'll have your Feej in condition to get to everything in short order. h34r:

 

[RadioHowie]

Shee-it, man......what the hell you doin' up this hour?
Only reason I'M up is a call from the office with computer problems I had to fix over the Neenernet with Remote Desktop.

Of course, I HAD to check my email to see what foolish Feejers were reading posts this time of night morning.

GO TO BED!!! I am.

I'm in Central time, wasn't that late!

But I did retire immediately after that forum session.

I forgot...you're on the wrong side of the Chattahoochee River bridge.