07 apex rpm's very low and stalls when warm on idle

[nate007]

I read in these posts a number of comments about cold start stumbles and roughness. I was told by my shop that the cold start idle is controlled by the knurled black knob on the end of a small manifold on top of the motor. I was told the knob only controls the cold idle. When the machine is warm and the idle drops, hopefully to normal, the cold idle circuit is no longer used. When I read comments about cold idle roughness, it makes me think the adjustment of the black knob is what should be changed. Once the machine is warm, it sounds like the low idle issue is probably due to the co settings. Two separate issues i'm guessing.

Both comments are partially true with the black knurled knob. The knob will adjust idle speed both when cold and warm. Depending on what year your Apex is, (if I'm wrong here, someone correct me, my sled is pre-EXUP) I believe all of the "pre-EXUP" 4cyl models have a thermostatically controlled idle that simply opens an air passage when cold and allows the idle airflow to increase, similar to holding the throttle open. I think the EXUP models use a stepper motor and controll idle electronically, like the Nytro and other 3cyl sleds.
Adjusting the knob will adjust the overall idle speed for all temp ranges though. If you adjust it up due to a cold low-idle condition, you'll likely have too high of an idle after warming up.
If the sled was running fine before and now it's having idle issues, I'd start with all the usual general maintainence first. Plugs could be a culprit pretty easilly, as could dirty injectors. Run some Seafoam through for a full tank and see if it helps. It might be a little rough during the tank though if it's actually cleaning something out. For those of us who have sleds that are more than a couple years old, age related issues can present themselves more and more, and with as intricate as the engines are, it doesn't take much to have you chasing your tail.
The CO adjustments are basically idle mixture adjustments up to approx 3000 rpm, and since there isn't an 02 sensor fedding signals to the ecu, these are preset from the factory. Thats not saying that there isn't a benefit from adjusting them, but don't rely on that as your first step.
If the annual service and making sure the injectors are clean doesn't solve the problem, you could have an issue with the idle control valve. There could be foriegn debris blocking one or more of the small hoses running from the idle control valve to the tb's, or one of the brass hose barbs on either end could be having a corrosion issue that's blocking even the smallest ammount of air. Even if your sled is stored indoors, humidity can still affect those tiny orfices. These engines need a surprisingly small ammount of air at idle, so the passageways are very small, and any tiny blockage could drop idle rpm's signifigantly. Carefully remove each hose one at a time and check everything carefully for age cracks, kinks in the hoses, and any obstructions. These are what the sled idles through as the main throttle blades are fully closed at idle.
If that doesn't solve the issue, there is likely an issue with either the idle air distribution block (the part with 4 tiny screws on the t/b) or the thermostat valve (coolant hoses running to the t/b). The distribution block needs to be synchronized with a vacuum gauge, and should only be messed with if you are fully confident with what you're doing, as you could likely cause yourself more problems. Get the factory service manual information and study it to help you diagnose your issues.
If you need the manual, send me a pm with an email address and I can send it to you in a zipped file. It's a pretty large file as the manual is nearly 650 pages, so I might have to send just the part you need.

 

[youngdman]

My dealer said it's a valve issue. He recommends opening the valves up for a little more clearance than what Yamaha specs call for along with cleaning/syncing the throttle bodies and you should be good to go.

 

[nate007]

Be careful when adjusting the valves open, a you may have to adjust the Co settings again. If you're comfortable messing with then that's good, otherwise let the dealer do it. If you have an afr gauge on it, that will help, otherwise it may take a little bit of messing with it to get them right. I'd try cleaning everything first and try that before adjusting, especially if it was good before.

 

[TBay Sledhead]

I tried all of the cleaning and checking, The CO adjustment did it for mine.

 

[Rich Kay]

I tried all of the cleaning and checking, The CO adjustment did it for mine.

What were your CO settings at with the problem and in which direction did you go with the CO settings to fix it ?

 

[CaptCaper]

Most seem to go to the - side. I saw some that went to -15. I'm going to try it as well. Mine with only 800 miles (bought used) did it. Once warm and or taken the idle good runs like a raped ape. So mine is a cold start in very cold weather only.

 

[TBay Sledhead]

I think I went to -10 but not positive. Sled won't be in the garage for a week or so, but if I have time tomorrow I will check. It's kind of a trial and error thing.

 

[CaptCaper]

I think I went to -10 but not positive. Sled won't be in the garage for a week or so, but if I have time tomorrow I will check. It's kind of a trial and error thing.

-10 might be a good starting point. I am very busy until Thanksgiving and without snow or frozen ground I'll tear up my yard getting the machine into the shop. I'm basically ready except for a trial of the CO adjustment. So it waits..soon though it's coming.

 

[youngdman]

Be careful when adjusting the valves open, a you may have to adjust the Co settings again. If you're comfortable messing with then that's good, otherwise let the dealer do it. If you have an afr gauge on it, that will help, otherwise it may take a little bit of messing with it to get them right. I'd try cleaning everything first and try that before adjusting, especially if it was good before.

It wont be me adjusting it that's what the dealership is for........

 

[Grunter]

I suspecting the ethanol in the fuel(same as it blocks the pilot jets on carbed machines) well if the small bleed holes get plugged on your injector feed - this alters the idle when warm making the machine too rich. I did the same as Gukrokit above and has helped a lot. you may want to play with your idle setting to fine tune afterwards..I'm thinking that blasted ethanol is mucking it up. On all my carbed motors - cleaning out the pilots or replacing them solves the problem instantly. I just don't have the tools to set-up the machine after I would clean the bleed holes. So I've stayed away and not addressed it any further.
I just hate taking it to a dealer and have the try this, that and the other thing. The stator plate thing is not related. I changed mine out recently cause it was fried. They all eventually fry up with next to no warning..Symptoms is bad running/starting - then before you know it it just dies.

I strongly suspect that the ethanol is plugging up the bleeders - which are cleanable - one has to just do it themselves or bring it in to a trustworthy dealer that is not going to side step the issue and want to change plugs, sync the throttle bodies(quick tune up) and not address the issue at hand. Most dealers I believe have not really addressed this - because I've talked to a few and you guessed it - it only happens to me and no one else they know has had the issue.

It's a problem for sure, to me it's fixable, but your bleed holes need to be cleaned - I'm almost 100% sure of myself. So far I'm buying time doing what most have done through the diagnostic gauge. People are selling their 100% good sleds for what is this simple problem! I've thought about it myself..
It's too bad Yamaha doesn't just say - yeah we know what it is - bring it in we'll fix for say 400.00 dollars or something. But I had the pleasure of spending already 500 at a dealer for him to install a washer in my secondary claiming the secondary was too tight and dragging down the idle. Well I was pissed and the next time it did it - I removed the secondary all together to see if that claim held water - it still did it! So I went into diagnostic and dialled back my numbers..I had mods that needed 10-13 before now at 8'ish. Runs pretty good - so play with that - when this phenomenon starts it changes yearly a bit as your bleed holes get more and more blocked(enriching your machine) so dialing down the adjustment will help - but at one point it won't work anymore..

My 2 cents

 

[nate007]

Grunter. They're air bleeds only, there's no fuel through them. All it does is meter idle air around (past) the throttle blades.

 

[guardrail]

If there is less air around the the throttle blades with the same amount of fuel, wouldn't that make it richer?

 

[nate007]

I'll assume I understand what you're asking, and that is assuming there is a blockage that it will be tighter at idle? Yes, that's true if that's what you're asking. There is actually less airflow to the motor when its cold that at idle when warm.

Basically, the throttle blades close completely and allow no air through at idle. When the tps sees that position, it only fuels what had been programmed for it to run at idle. The idle system only lets air in from the airbox and meters it into each throttle bore behind the throttle blade. (aka-air bleed).
Generally the calibration is such that when the air bleed is open (cold) it lets a little less air through it to make the mixture richer. As the sled warms up and oil flows better, pistons warm up, and the engine spins easier, the air bleeds open up and and it leans the mixture out a little. This is why you'll notice that if you try to rev a child sled it has a bog or hesitation right off idle. The higher startup idle when cold is caused in part from the spark being advanced at colder temps as well as the richer mixture from less airflow, similar to closing a choke butterfly on a carburetor. It can seem somewhat backwards to how you would think, but it works.

 

[guardrail]

That's how I thought it worked. I had just read through all ten pages of this and must have missed the part where Grunter suggested ETHANOL might be causing the blocked bleeders. Once I read his post again your answer makes perfect sense.
My bad.

 

[Grunter]

I'm so aggravated by ethanol effects. Would it be possible that spit back gets at these air bleeds or can they be blocking for corrosive reasons? I figure like what you just said if the holes are blocked(slides closed) and sled idling it's not so noticeable at cold start idle because the throttle position sensor also cracks the throttle a bit when cold to raise the idle. when it warms up doesn't it close the blades then also rely on the bleeds more to lean it out as you say?

I believe it's gas/fuel related..maybe the TPS could play a role in there too. I changed one on my mustang because it was getting sticky(if I'm seing a pattern here) it's sleds with roughly 8,000+ kilometres that seem to act up and get worse as time goes by..

Does this makes sense?