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I'm with BPS, swap before you buy, but I'd probably do the ECM first. I will add that I seen on the OTB page a quote from a Polaris service manual, “80% of all EFI problems are caused by wiring harness connections.” just something else to ponder...
 

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‘17 Ranger 570 Midsize
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it’s no theory, it’s proven fact around here that you don’t run high ethanol fuel in the winter time even my local dealer has been pushing that fact as well.
What is your elevation? I'm 4000-4500 and don't have your issue. But also I'm not in an area with the Winter blend ethanol fuel either.
 

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Have run premium, non-ethanol with stabil for 5 years in my 2017 900 XP EPS and it starts and runs great in any weather. It has been down to -17 in years past and always fired right up. I also run fuel injector cleaner through it once a year. Just a suggestion.
 

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2015 Polaris ranger 570 XP
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4,156 Posts
Have run premium, non-ethanol with stabil for 5 years in my 2017 900 XP EPS and it starts and runs great in any weather. It has been down to -17 in years past and always fired right up. I also run fuel injector cleaner through it once a year. Just a suggestion.
Same here with the exception of the annual FI cleaner. I did run some Seafoam through it once and it wouldn't hurt to do it again. I've never had a starting or fuel problem but on three wide spread occasions I've had it shut down when cold after start up but after restarting no more issues.
I have no idea why it shut off on those 3 occasions, it could have been a ECU problem (momentary brain fart), maybe a sticking compression release or even a piece of carbon stuck under a valve seat which cleared itself upon restart. I never investigated further since the occurrence was so seldom.
 

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Discussion Starter · #28 ·
So after my most recent troubleshooting, I swapped out the complete throttlebody fuel pump, fuel injector, crank position sensor, and finally ECU. fuel pressure was low and I think it is running slightly better, but still wants to die cold. Spits and sputters. so I finally broke down and sent it to the dealership. They are going to try to re-flash the ECU. But the mechanic is fairly certain that the valve guides are gone in the cylinder head says he’s seen it multiple times with guys running 91 octane fuel, where it will burn the ex valve guide out of the head . And of course, after trying to swap, ECUs, the donor vehicle ECU failed on me about an hour later so if anybody has a 570 ECU laying around I would love to buy it off you.!
 

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Let us know if valve guides were the issue. Hope you get it resolved soon.

I'm going to guess guide wear from running 91 is due to carbon build up?

Back in my sledding days....2 strokes. More octane than needed resulted in more carbon and less cleaner burn and more deposits.

I'm guessing the same may hold true to our rangers.

Never ran anything other than 87 in my rangers since 2004. Never a fuel related issue.
 
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