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Discussion Starter · #1 · (Edited)
Hello i have yamaha r6 2003. After i bought i leave motorbike in service to do main things:
- valve clearence
-new timing chain
-new oil
-new spark plugs
It was arround 2 years ago.
Since 1-1,5 year i have a problem. As i noticed, when temperature outside is warm and engine is hot the idle speed is waving and often in the end engine dying.
TPS sensor returns values 15~16 - 95~96 in diag menu.
When i run engine in garage the idle speed are waving and engine dying when water temp is more than around 85℃ (185℉).
Few Days ago i noticed this problem also on cold engine. I started engine, and the idle was lower and lower and finally died, after this was a problem with Run engine again, after few secs i was Ale to start engine. Smebody know where can be the problem ?
May be service mistake ?
After i got back motorbike from service airbox was loose between throttle body.
 

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Check for stored codes. Could be vacuum leak. Read vacuum to be sure. Otherwise you'll need to check for fouled plugs. If the plugs are fouled, you'll need to tweak AFR. More details are available upon request.
 

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Discussion Starter · #3 ·
Check for stored codes. Could be vacuum leak. Read vacuum to be sure. Otherwise you'll need to check for fouled plugs. If the plugs are fouled, you'll need to tweak AFR. More details are available upon request.
-In menu are no stored codes.
-How to check vacuum leak? I have only one vacuometer so i set cyl #3 as in service manual and i built simple vacuometer with interconnected on the bottom 4 pipes and filled with oil(someting like communicating vessels) and each pipe was connected to each sync pipe in throttle body. I tried to synchronize throttle bodies but when engine is waving the vaccum jumping and its not possible to set properly. One time i managed to set properly synchronization but when started waving idle as before vaccum was jumping.
-I unscrewed plugs and they are black ( im not sure if the reason can be because engine was working a lot of time on idle when i was trying to sync throttle bodies ). The plugs was screwed by service and when i was unscrewing they i havent to use a lot of power to do it. The metal seal on spark plugs was not crushed. Is it possible they was screwed too loose and engine when was hot the plugs was just loose ? For example when was autumn and was not hot outside engine was working good i suppose because engine not cross some temp level.
-I heard i can change AFR in CO menu next to Diag for each cylinder separately but i don't know how to set it and check whether current values are default values.
 

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Did tightening the plugs work? I once had a bad spark coil that would quit only when hot. That took a long time to diagnose. With enough throttle I could get it to run rough on 3 cylinders but once it passed 8k holy "S" I was instantly back to full power and holding on. My guess is they diesel after 8k, but don't pull a me and ride it home on 3 cylinders as I'm pretty sure that's what caused my connecting rod bearing to fail.
 

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Discussion Starter · #5 ·
Probably i resolved the issue. When i tightened spark plugs with the strength as in manual the issue still was ocuring. Resolve of this issue was the air screws in throttle bodies. My air screws was screwed almost to the end( two of them was screwed to the end rest of them almost) and the vaccum was as in manual. BUT i noticed the engine works a lot better when the screws are more unscrewed so i unscrewed a bit each of them the same amount of turns. The vaccum is still the same as in user manual and engine on idle works perfect ( like some offset, the vaccum can be the same when the air screws are screwed totally and the same vaccum is possible when the screws are unscrewed for example 3 turns). Probably this screws adjust not only vaccum but also some fuel/air mixture? Am right ? Somebody know how to set properly screw #3 because it have to be a reference screw, so i think should be some way to set it properly.
One question. When the exhaust is not oem - the air/fuel mixture should be more rich or more poor? I wrote email to yamaha service about the CO menu settings. They told me original the values oscillates around 0 but when i have changed exhaust it should be between +10 and +20.
 

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For second-gen, I don't believe that the air induction system affects performance because there isn't an oxygen sensor in the exhaust. The ECU doesn't self-tune based on oxygen sensor feedback. That was the concern is the diluted exhaust output would make the sensor return lean readings back to the ECU. (though engineers would've accounted for that)

377551
 

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For second-gen, I don't believe that the air induction system affects performance because there isn't an oxygen sensor in the exhaust. The ECU doesn't self-tune based on oxygen sensor feedback. That was the concern is the diluted exhaust output would make the sensor return lean readings back to the ECU. (though engineers would've accounted for that)

View attachment 377551
That paragraph in the manual doesn't clearly say where the air is supplied to. It sounds like intake, but it doesn't make sense because it's supposed to burn off excess exhaust charge. (Can somehow with their engine apart confirm where these AIS ports lead to?)

I have been having same issues. Starts and runs fine, but once a week or so, when I coast down to a stop and press clutch or put in neutral, the engine dies. It looks as if it's not getting enough air. The only way to keep it running is to hold it at a high enough RPM so it won't die. Synced the throttle bodies a few times within the last 2 months too.
So I just re-installed AIS today and cleaned TPS and just got back from a ride. No stalling (fingers crossed!). That might be the culprit. Time will tell.
 

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377556

377555


The idea is merely to dilute the exhaust with fresh air in order to meet emissions standards. It's kind of like watering down your moonshine in order to make the alcohol content legal. (cheating) My previous car would do the opposite, and recycle air from the exhaust, back through the intake.

The reed valve would only allow flow in one direction... from the air-cleaner and into the cylinder head.

What I don't understand is how the air, entering the top of the valve cover, ends up in the exhaust. (I never looked that closely at it while I had the valve cover off for valve lash checks. -- wish I had) If it never enters the intake, bypassing the cylinders entirely, heading straight to the exhaust, then for 2nd-Gen it would have exactly zero impact on idle and performance what-so-ever. If this is being routed through the intake then it could be relevant/impactful for idle; and cold-engine acceleration/cruise. If it's malfunctioning, allowing flow when it shouldn't on a warm engine, it could be affecting all manner of operation except WOT where presumably there's not enough vacuum or negative pressure to pull open the reed-valves.

It's easy enough to eliminate this as a factor by pulling the hose off the front-right side of the air cleaner, capping-off the air cleaner and plugging the hose. That would take five minutes.
377557

Vacuum cap kit.
 

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I thought the reed valves fed air into exhaust ports given the way it was described in the manual, but I need someone who has their head taken out to confirm.
Or at least, someone with their headers removed can look into the exhaust ports.

PS: Another reason I believe the AIS feeds the intake (not exhaust) is that the air supplied to the AIS comes from the airbox AFTER the filter. The AIS nipple on the air box is on the filtered side. If the AIS fed exhaust ports, then it wouldn't need filtered air. Just leaving the reed valves exposed to the air would have been sufficient.

PS #2: I rode this morning for about 45-50 mins. Idle is steady, no fluctuations, and no stalling.
 

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Yeah it wouldn't make sense if it were routed through the intake and cylinders. It'd be like intentionally adding a vacuum leak (unmetered air). So I think our original assumption of it heading straight to the exhaust is likely correct. But in that case, it really shouldn't affect your idle given that a 2003 model wouldn't have an oxygen sensor in the exhaust.

EDIT: Filtered air is better for the catalytic converter.

Never mind about the unmetered air comment as this is a MAP sensor setup; not MAF.
 
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