Polaris UTV, dont know the exact size, it belongs to a neighbor of mine. 2 cylinder, fuel injected. He knows i tinker with bikes and brought it to me after he's spent a shitload of money at a "dealer" and they havent solved the problem, they just keep throwing parts at it. So far: Just did the XXX mile service on it, which included plugs and air filter among a few other odds and ends (owner is NOT the mechanical type person). at idle as well as low speed under load (driving) it has a pretty bad stumble, almost like its either a fuel issue or a vacuum leak sucking too much air. He took it in with this problem and for several hundred bucks they replaced the fuel filter/fuel pump and said it was fixed. He left there with it on the trailer (dealer loaded it up), then he drove 100 miles to go hunt, and pulling it off the trailer, it was still doing what he just paid to have fixed. He took it back when he got home, and they claimed it *may* need new injectors ($600). They claimed it was running perfectly with the new fuel pump when it left but the issue is still there. Things *I'VE* done to try and find the problem: checked battery for good voltage (12.4 not running, 14.4 running) batt. is good. checked fuel tank, clean as a whistle, and i can see where the fuel pump/filter is brand new. checked all air lines/hoses/filter and everything looks great. He has NEVER ran any type of ethanol treatment in it, so i told him its possible the injectors may need cleaning, but probably not replaced. He actually found a pair of used injectors on ebay for $50, installed them, and the problem still exists. I told him THOSE injectors are possibly clogged as well, ya just never know. If Melka/ProFlo cleans these types of injectors, they will be sent to him to be inspected and cleaned. My question is, wtf else could it possibly be? I mean, the fuel line from the fuel pump to the injectors is 2 feet long, there just isnt much TO this damn thing, but after driving it today, it DEFINITELY has a really bad stumble at low RPMS under a load, and just a weak stumble at idle. Put it to the floor and get to higher speed/rpm's and it seems to run fine. I'm stumped.
With FI, any number of sensors can cause issues (crank/cam sensors, TPS, idle air motor). TPS sensor are usually easy to verify with a multimeter. Make sure at X% throttle, it actually tells the ECU it's at X% throttle. Idle air motors can be more difficult, but problems like that are usually with something clogging it. A clogged IAM can sometimes seem like a vacuum leak. Is there an error code system on FI on that thing? No codes I assume though or you'd probably mention it... Maybe take the throttle body off and clean out all the passages, checking the sensors on it with a multi-meter against the manual's values. Oh, and if it has a MAF, check that to see if something is wrong with it, they fail regularly. Not sure if it's a MAF or MAP based engine in it though. I don't imagine the injectors are clogged if it runs fine at higher speeds / loads. Well, there's my ideas, having 0 ZERO knowledge of Polaris UTVs...LOL.
Sounds like it's lean at the problem rpm and throttle position. Try covering part of the intake or air filter and see if it gets better or worse. If it gets better, then you have to figure out what's making it run lean.
i have zero knowledge of them as well, and i dont have a service manual and i KNOW he doesnt. LoL If its one of the sensors, then he's just going to have to take it to a different dealer and demand some answers, which i told him i'd be happy to go with him. Rick, i'll see what i can do on that. All this is under the seat, and will be hard to do while driving it. Most everything is sealed pretty well as this is a UTV and gets pretty wet and muddy in there.
If he's been running ethanol gas in it with no treatment I'd start there. I'd completely drain the tank, take it out if you have to, to get it all out. May be a layer of ethanol and another layer of water in it. I see issues like this all the time and it's usually because of the shit that comes out of the tank. Catch it in clean clear jugs, you might be amazed at what comes out.
i think i can access the utv service manual (we're a victory/indian dealer) and could possibly be helpful. pm me if you want. i'll need year, model and miles.
Not yet. Been out of town the last couple of weeks and haven't had a chance. First thing I'm gonna do when I get it from the neighbor is dump the fuel, refill with non ethonal fuel, run a can of sea foam thru it and do a more visual search for vacuum leaks.
The air box system really sucks on them, seen people complain about the RZR sucking the stock filter in on itself. Also the throttle cabling has been know to stretch(could be one opening before the other). Basically throttle out of sync. Strange leaks around the airbox also. Might just be crappy stock FI map. Check to make sure the clutch is not dragging, people always mess with the clutch for fast lock up but mess it up.
For sure check the position of the TPS. Some Polaris engines are really sensitive to it. I had a sportsman 800 efi ATV that the TPS needed to be adjusted. Had a bad idle but ran fine at higher RPM. You can do it just by ear. Have someone put foot on brake and put it in gear (so it idles down), loosen (not remove) the TPS sensor screws and move it very slightly until the idle smooths out. (Mark where it is with a paint pen before you move it so you can always go back to the OEM setting for reference. Tighten back down and blip the throttle a few times and make sure it idles back smooth. May take a couple times. I have seen the local Polaris tech do that on a lot of units over the years. He can get it perfect no volt meter needed. As others said, check for intake leaks. Some of those UTVs have some crazy intake setups with lots of bends.
i bought a 2010 ninja 250 with 600 miles and it had the exact problem i thought it was dirty carb i cleaned it nothing changed. someone on the ninjett forum then sent me a set of perfectly working carbs , and still no change... it had to be some kind of vaccum leak once she got above 6000rpm it was fine. i then brought it to a local tuner he cleaned the carbs put his jet kit in and fixed the problem but never said what it was.. i didnt mind but i think he just wanted to sell the jet kit service and install then a simple fix but that was such a headache i didnt mind
If it wasn't an ATVand wasn't fuel injected and used a magneto with two coils ...I would guess failing low speed coil in the ignition. parillaguy
