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Discussion Starter #1
Hey guys,

My 2004 R6 is unstable at idle speed. It drops to ~1000rpm from ~1300-1400rpm for some seconds and it seemed one piston is not working properly. When I start moving, under 3000rpm it shake a bit but above it goes back to normal.

I changed the spark plugs and after that it was working normal again until yestarday. After a ride, we stopped, it was unstable again. I shut down the engine and when we start moving, it was good again.. Today I test drive and was good again.

Do you guys had a similar problem before? I don't know what can cause this.. coils? injector?
 

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Touchdown!
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You can always test different things. Start with fuel injection cleaner and a fresh tank of the fuel.

Also, check you air filter and box for debris. And, test your coils for factory spec resistance. It could be an electrical ignition component which has wore out from heat over the last 15 years or so.

If problem continues to exist, then we can continue with a deeper diagnosis. There are also some threads here which has discussed this over the years. I would help you search for it, but I'm really busy right now multi-taksing.
 

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YZFR6... ooodles of HP
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Yep, fuel or spark related.
 

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Discussion Starter #4
I checked the coils again and I measured the resistance but all have a good value.

I found out that one coil cant be pushed in completely. I think its got some water when it was raining and corroded a bit. I will replace that one and clean that hole and see whats gonna happen.
 

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Have you changed anything on the bike recently, particularly with the exhaust? I've had what you describe happen on bikes with cat-deletes and no A/F fix. They run fine for a few 100 miles on new plugs and then start dropping below 500 idle and generally run like crap below 6k. Coils going bad usually cause hot start issues so I doubt it went bad. Could be a piston ring starting to go, that would explain the vibration. Can you do a compression test?
 

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Unfortunately, measuring resistance on the coils has proven to be ineffective. Had to use a spark gap tester in diagnostic mode to spot my bad coil. They're not firing under a wet 12.5/1 compression so they all still fire with 100% consistency at massive gaps. It's the one that fires unreliably at a fraction of the gap of the others, that is the culprit... the outlier in other words, is your bad one.
 
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