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Attak low on power and misfire on hard acceleration


Ok, while changing my plugs I decided to check the ignition coils. All four had a .17 olms, which is in spec for Primary coil resistance. The secondary coil resistance is supposed to be between 5.0-6.8k, all four of mine said 9.4k. Not sure if I did something wrong or not but they all came out the same although high (even tried warming them up). Disconnected the magneto coupler to check the stator coil also, that was supposed to be .19-.24 olms & my multimeter said .5 olms. I checked the plug below that one which I believe is the pick up coil with the two wires, I got no reading at all.
sideshowbob, if you or anybody have any ideas about these results please share, thanks :)
 
I checked my coils already and the primary and secondary fell within specs on all four,
The fact that all 4 of your coils were the same would indicate to me that your meter may by slightly inaccurate.
I have not tested my stator or pickup yet and won't be able to for a week or so.
 
sideshowBob said:
I checked my coils already and the primary and secondary fell within specs on all four,
The fact that all 4 of your coils were the same would indicate to me that your meter may by slightly inaccurate.
I have not tested my stator or pickup yet and won't be able to for a week or so.
Click to expand...
Did you find anything with the TPS? wouldn't be the air temp sensor would it?
 
The airbox temp sensor was one of my suspected culprits but its readout matched the actual air temp when I did a diagnostic on it
I am waiting for the new TPS to come in...hopefully thats the problem.
I will post the results when I get it installed.
Thanks for the ideas...keep them coming.
 
I started having this problem today as well??? It feels as though there's stutter when i step on it. It's not all the time but fairly frequently. I am fairly new to the sledding world and more specifically, Yamaha Apex sleds.. I just got it (2009 LTX) and am a bit bummed out that basically on my 4th run, this starts to occur.
 
Obviously there are quite a few of us with a similar issue on our Apexs...seems to be on the pre 2011 models so far.
Hopefully we will get this solved.
 
Questions for Apexs with similar issues:
-what year is your sled
-how many miles on sled
-has the TPS been updated
-has the stator been updated
-what spark plugs are you using
-any airbox mods
-do you have a fuel controller
 
sideshowBob said:
Questions for Apexs with similar issues:
-what year is your sled
-how many miles on sled
-has the TPS been updated
-has the stator been updated
-what spark plugs are you using
-any airbox mods
-do you have a fuel controller
Click to expand...

-2006
-9700 mi
-not sure
-not sure
-NGK cr10ek
-Bullseye filters in lid
-no

I bought it with 9k on it and put 700 on it this season, It developed this issue about 150 miles ago. I did maintenance on it when I bought it, oil change, and adjusted nearly everything to my liking. The plugs are new but that is what the previous owner/owners had in it and they looked old.

I did some diagnostic checking per your suggestion earlier in the thread and the TPS reads good but the air box temp sensor reads 98 with a cold sled and an ambient temp of around freezing, so I'm ordering one tomorrow to try that.

It seems to me that these things are very technical but will make adjustments to run in almost any condition, so I would bet that these problems stem from something sensor or ECU related. I did read that my faulty air temp sensor would throw the ECU into a base setting so my misfire issue could be better or worse depending on the outside temp. It seems to be worse the warmer the outside air is, really bad yesterday and it was almost 40f here.
 
Zachary said:
-2006
-9700 mi
-not sure
-not sure
-NGK cr10ek
-Bullseye filters in lid
-no

I bought it with 9k on it and put 700 on it this season, It developed this issue about 150 miles ago. I did maintenance on it when I bought it, oil change, and adjusted nearly everything to my liking. The plugs are new but that is what the previous owner/owners had in it and they looked old.

I did some diagnostic checking per your suggestion earlier in the thread and the TPS reads good but the air box temp sensor reads 98 with a cold sled and an ambient temp of around freezing, so I'm ordering one tomorrow to try that.

It seems to me that these things are very technical but will make adjustments to run in almost any condition, so I would bet that these problems stem from something sensor or ECU related. I did read that my faulty air temp sensor would throw the ECU into a base setting so my misfire issue could be better or worse depending on the outside temp. It seems to be worse the warmer the outside air is, really bad yesterday and it was almost 40f here.
Click to expand...

Great info.
My sled seemed worse in warm weather as well
Sounds like you definitely have a temp sensor issue...mine tests OK but maybe it's intermittent...I have a spare up modified airbox that I can rob the sensor out of when I get the new TPS installed and if problem persists. I also had the CR10 plugs but am installing new 9s
 
sideshowBob said:
Questions for Apexs with similar issues:
-what year is your sled
-how many miles on sled
-has the TPS been updated
-has the stator been updated
-what spark plugs are you using
-any airbox mods
-do you have a fuel controller
Click to expand...


- 2009 LTX
- About 8600
- Unknown
- Unknown
- Unknown
- Unknown
- None that i can see
- Doubtful

It's a stock machine that i bought in October. All service/maintenance requirements were done at that time (I.E donuts, etc...). It ran without issue for about 500 miles and then this started on Sunday. I was out for about 120KM last night and it only did it a few times but then again, i was not hammering the throttle much either....
 
Air intake temp sensor didn't help. TPS tested good, injectors and ignition coils tested good.
What should the air pressure reading be in diag mode? do they do it in inches or what?
Changing the fuel CO in diag mode richer helped some, but still it's bad off idle when you "whack" it.
 
Finally had time today to work on the sled.
Pulled the plugs and all four of them are black and sooty...obviously sled is running rich.
I had the NGK CR10EK plugs in and I replaced them today with the stock CR9EB
I installed the new TPS and calibrated it. I had to set the throttle closed at the max 18% to get 96% full throttle[this is with the PCV controller bypassed]. Before the new TPS my Readings were 15 % throttle closed and 88 % throttle full open, again with the PCV unplugged.
I will update when I get it all back together and ride it.
 
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