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Misfiring please help!

  #1  
Old 05-20-2010, 11:40 AM
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Default Misfiring please help!

I have an 02 f4i with 16k miles. Mods are a yoshi slip on, and a yoshi power commander. I have had no problems whatsoever although yesterday it started misfiring. I was cruising in 2nd and all of a sudden it felt like it was only running off of 2 or maybe 3 cylinders. Sounded like a subaru . I shut it off and turned it back on, and bam it was back on 4 cylinders and was fine. Today it felt low on power on the freeway, so I pulled off and it definitely is misfiring pretty good. On decel I get some loud backfires that I have NEVER experienced before. One cylinder definitely seems to be misfiring when under load. Edit, I do have 16k miles and I have never checked the valve lash. Could that cause a problem? I'm not sure if it's in my head but it seems like there is more vibration/noise from the engine, def not the CCT. Would improper valve clearance cause that?

I do not have much experience with bikes, but am very mechanically inclined and can fix it if you guys help me out with where to start.

Any known problems like this?

This is my commuter so I can't afford to not get this figured out asap.

Thanks!



This is my commuter so I can't afford much downtime
 

Last edited by GDM YO; 05-20-2010 at 11:44 AM.
  #2  
Old 05-20-2010, 12:00 PM
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Pull your plugs out, and see what they look like. More then likely you will have a problem with either a plug or one of the coils. Make sure you don't have any moisture down in the plug galleys. A fuel injector could also be the issue. I wouldn't think your problem to be base engine since it is intermitten, but could possiably be a sticking valve in the head. Just my two cents...good luck
 
  #3  
Old 05-20-2010, 02:03 PM
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I'll check my plugs and coils out, unfortunately since it's intermittent it's hard to diagnose as idling it doesn't really always do it.
 
  #4  
Old 05-20-2010, 02:06 PM
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since its not a constant thing i would most def. bet its plugs or coils as stated above...
 
  #5  
Old 05-20-2010, 02:43 PM
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Are the coils known to go bad? I assume I should probably just replace all four plugs, especially with 16k on them. What do you guys recommend?

Again, I appreciate any and all of the help
 
  #6  
Old 05-20-2010, 03:02 PM
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I can't say for sure on bike's, but in the automotive world (I am a Ford dealer mechanic) I sure do replace a lot of coil on plug units. They are without a doubt one of the hardest working items on our bikes so I would take a gander, and say they are highly susceptible to damage. I do know for a 100% fact on autos they can be either highly intermitten or there all the time for what thats worth. They also tend to miss more when under a load such as being in the wrong gear trying to climb a hill.
 
  #7  
Old 05-20-2010, 03:53 PM
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I just re-read your OP, and missed the part about you having a power commander.....They CAN cause misfires, try disconnecting it and see what it does. Make sure you check the harness going to it VERY carefully for any damage or chaffs in the wiring.
 
  #8  
Old 05-20-2010, 06:12 PM
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plugs +1
 
  #9  
Old 05-20-2010, 07:25 PM
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16,000 is actually when the manual states you should replace the spark plugs.
 
  #10  
Old 05-26-2010, 10:46 PM
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I had the same problem with blowing out fire and running like a Subaru but mine also smelled like gas but no gas leak...found out that it was the FPR and replaced it myself yesterday...no longer smells like gas but still runs like it doesnt have any power https://cbrforum.com/forum/showthrea...533#post696533 check this maybe theres good facts about some common problems
 
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