850 Cutting out/bogging issue

[MTMike]

I picked up a used 2018 850 this year with about 1000 miles. It seemed fine on a 5 min test ride but didn't make it a couple of miles when I took it riding before it started running badly, topping out around 6k rpm--no check engine. A set of plugs seemed to make everything better for 500 amazing miles, what a machine!

Then the problem seemed to come back suddenly. The local dealer was over a week out so time to throw parts at it. Another set of plugs and new rave gasket (pita) and rave seals and it worked for 50 miles. It would run great then just drop off, coming back online and off, getting progressively worse. Check engine light was coming on but would come off at idle. With some more riding I finally got the code P0264--mag side injector fault. You can read the code by holding down the mode button and flipping the hi/low beam lever a bunch of times. I found that it was running on one cylinder--mag side only. The PTO injector was clearly the issue (based on unplugging each injector and running it). I finally isolated the issue to the plug/wires on the harness side of the plug and upon digging in found the wires each had failed inside the insulation back in the wiring harness about 2.5-3" back from the plug.

BTW, trouble shooting was pretty straight forward considering how much I loath electrical issues. According to the local parts guy the injector needed to have resistance below .27 ohms (as I recall, and both of mine read .24-.25) and the harness side of the plugs keep some voltage even after turning off the machine for an hour or two making testing easy with a multimeter. While riding I had taken off the hood when the error arose and, on manipulating the plugs and wires, had narrowed down where the issue was coming from. The plug contacts showed voltage until the problem had advanced and finally I was able to identify a fault on one of the feeds. After fixing it and testing I found the second wire (ground) also had an intermittent fault and cut the insulation away at the same location where the first had broken and found the conductor was burned away at the same spot. I do not know what could have caused both of these to fail at the same location or in this manner--there was no evidence on the insulation of a short, cut, or break. None. The hot wire had pulled out while I was cutting away the tape wrap.

My search on the P0264 code showed that others have had a similar issue but with more obvious failures in the wiring. Also of note, the code was for the mag side but the failure was on the PTO side. I think the machine had been suffering from a partial failure occasionally that would lead to plug fouling due to it burning too much oil without fuel.

I would like to bump into the guy who designed the hood system in a dark alley some time. What a pos. How could the same machine with the ingenious SHOT system be straddled with such a ridiculously sad design? Try pulling that absurdity off a few times to trouble shoot while out on the snow...

 

[Tylerdurdan]

Just paid the dealer 500 to put in a new injector and replace some of the harness. 17 850 sp

 

[MTMike]

Just paid the dealer 500 to put in a new injector and replace some of the harness. 17 850 sp

I was going to replace the injector as well but the dealer didn't have one in stock and it tested correctly (doesn't mean it was functioning correctly) and when I fiddled with the wires it would come out of the fault. That is why I posted this--my public service announcement. I'd imagine the problem, simple as it is, is causing some people issues. I've put about 60 miles on it the last couple of days and all is well so far.

What symptoms did yours show? Was yours an intermittent cutting in and out as well? Fouled plugs? Did it give a CEL?

 

[Tylerdurdan]

Yes it would cut out when trenched out going up hill or side hill i couldn't pin and wiggle had to get it level or facing down any other time ran good I could do long pulls but if I stopped or let off it would run good then bog and die in the upward position but now every time. p0273 would flash every now and then it was hard to catch. I would ride with my code setting on and I would catch a glimpse of it. But it was only some times and more frequent at the end of the day. https://www.snowest.com/forum/threads/bog-on-incline.458382/ this is my other thread with a video.

 

[worx53]

We have had similar bogging/ cutout issues - and many with no codes at all- with some its the fuel pump and some the main injector- ohms check ok but - if you have buds and can test the injectors with the machine off you hear a distinct thump when the injector is activated and a much duller/softer thump from the bad injector.

 

[Blk88GT]

Awesome post Mike. Thanks for sharing.

 

[Tylerdurdan]

Dealer replaced fuel assembly and fuel filter and took 7 gallons of gas, at least they left some $980 out the door. Runs good now.

 

[mtnxtreme1]

Im exsperiencing something just like your issue runs great at about 7 miles started setting check engine lamp then goes out no hard falt 2020 summit 220 miles
let it set for a few minuites starts runs good for about a mile then the same thing lose a cylinder or feels like it flashes check engine but then clears its in limp mode
have to shut it off and restart after setting for 10 minuits lhen runs good over and over still no hard falt

sounds like the injector wiring to me will check it this evening thanks Joel

 

[SgtArms]

mtnxtreme1 - I have the very same problem on my 2020 Summit SP 850. Dealer replaced ECU ($1500) and absolutely NO improvement. Runs relatively well under 50% throttle then bogs under heavier throttle. Random "Check Engine" display that goes away when throttle returned to idle. Restarting engine and process will repeat itself after a mile or two. Were you able to find the root cause?​

 

[bwar4]

Purchased a used '19 Summit XP 850 and have experienced similar problems. Sled ran great off the trailor, 10 miles in if you pin it it would bog, spit and sputter. Able to ride out but only 1/4 throttle or so, was not in limp mode though. Initially dealer told me it was my Stator, and $1,500 to replace. I bought a new one and did the work myself, saved immensely which was good because it made no difference. Took it back in and they said it was the crank shift position sensor now. Put a new one in and was able to ride once, no problems yet......

I did a bunch of forum reading trying to self diagnose, read a lot about fuel system. I did replace the internal fuel sock and external fuel filter while doing the CPS. May have also helped? Beings it was tore down anyway, thought I take extra precautions.

Bye the way, had the old stator professionally checked out and they assure me it is good. Oh well, glad I saved a little by doing myself.