Hey everyone, newbie to the site here. I've done some searching of other posts and didnt quite find what I needed yet, and my apologies if I missed finding the right one. One similar (and may turn out to be the same) post is over at "2007 700 sportsman rough idle backfire"
2007 700 sportsman rough idle backfire - Polaris ATV Forum

So here goes my problem...
2007 Sportsman 500 EFI... the problem I'm having is that I die/stall out trying to let it sit idle at its normal 1200-1300 RPM or run at any RPM less than about 2000. Running in the 2000-3000 RPM range is a bit rough. Running at >3000rpm is fine, but coming back down into low rpm will sometimes cause a light backfire (feels like its through the intake directly under my seat)

Started having the problem 2 weekends ago when the fourwheeler sat outside at camp in 20 degree temps for the first time since I've had it (garage kept since I bought it used ~6 months ago). Got home from camp, looked at the spark plug and it was completely fouled up (black, dry fouled). Put a new plug in and it ran alright for a day or so. My original thought was maybe a little water in the lines, froze just enough from sitting outside and made it run pretty hard at camp. Would've made enough sense to me, even though I did throw some gas anti-freeze in at camp.

Then the problem resurfaced - even after being back in the warm-ish garage.

I can start the fourwheeler with the throttle partially applied... essentially getting it right up to 3000rpm. But as soon as I let the throttle out enough to get the RPM down below 2000 it stalls out.

I've been putting the battery tender on it at nights while I've been diagnosing the problem the past couple days, but that hasnt noticeably changed anything. I do take the tender off when I start working, and it measures right about 12.8 or 12.9, but I keep forgetting to check after awhile. Weak battery could've also surfaced the first time in cold at camp??

I saw AKStew posted about checking the t-bap sensor. Is this something I can do at home, or is that a shop only thing?

My only other thoughts are either the fuel pump starting to go bad or maybe even a borderline weak battery (even with the tender)?? Another post suggested needing to have the computer reflashed??

Can anyone confirm these thoughts or point me to something else?

Appreciate your folks' time!

 

My guess is the throttle cable at the handlebars needs adjusted,you could also have a dirty air or fuel filter.

 

I've adjusted the throttle cable up and down - didnt help.

The air filter is relatively new, and I even tried running with no filter there just for the heck of it to see if it made a difference - it didn't.

The fuel filter is still on my short list of things to try, unfortunately, I haven't had time to tear the front plastics off to do this yet. I haven't done the fuel filter swap/change out before on a Sportsman - any tricks I should know?

 

Welcome to the forum! You might also check the expert section "sticky" about the t-bap sensor harness problem,especially if your atv is back firing and the idle is erratic. OPT

 

Maybe this Video: Polaris ATV Thumb Throttle Maintenance Tips | eHow.com

 

my bike just started doing the same thing can you tell me what the problem was please.

 

The most common problem at idle on the efi machines was the map sensor wiring harness and sometimes the harness connector itself can have the wires slightly pulled out. The wires can be complete with no bare spots but can break internally. The oem harness repair kit is #2876315, but if they haven't upgraded the wiring you will get the same gauge repair kit. You might check ebay on improved kits if they have em plus look at the "sticky" in the expert section about tbap and map sensor wiring problems. OPT

 

I agree with OPT. Check the wires on your map sensor. I recently had the exact same issues you are describing and found that one of the wires was broken internally about a 1/2" from the plug but showed no signs of a problem other than the fact that the wire was stretchy like a rubber band which is a dead give away for a break. I bought one of the harnesses from the link in the sticky and will say they are definitely better quality than the oem repair kit and should be problem be for a very long time.

 

I actually believe I had 2 problems that were contributing to my back firing and stalling.

First, and I think the greater issue, was that my stator, bendix and whole recoil starter housing was rusty inside. Apparently the previous owner had dunked it in water and not dried it out well enough. Everything was incredibly rusty, leading to the stator not recharging the system well enough - especially in the cold conditions (I guess?). Took the side off, sprayed a bunch of brake cleaner in there, wire brushed what I could, and in general cleaned it up. Even took the bendix out and got that nice and shiny while I was in there.

Second, was my fuel filter. I pulled the old one out and it was nearly completely clogged - again from the previous owner. Not sure how it got so bad to be honest... Put a clean, new one in and the machine was running much better.

I also did some other general maintenance along the way, but I dont think any of those things were overly helpful to this issue. Just getting the bike nice and cleaned up to my liking after it was minorly neglected by the previous owner.

I also agree with the last 2 posts as well.. that map sensor wiring harness could definitely be the issue. I definitely wouldn't bet against it. Do you notice the stalling issue when turning one direction more? i.e. always turning right/left makes it stall? Could mean a wire is broken, but the connection is there going straight, then when the steering column is turned the broken wire disconnects just enough...