2006 500 EFI. New plug gapped correctly, new air filter, fuel filter. In the morning it runs fine. After 2 hours the problem begins. It starts missing, then sputtering, then backfirin all the time, not just when going down hill. By the end of the day, it wont even idle. Took it to Polaris, they could not get it to do anything in 30 minutes so they gave it back to me. What is it that it will run fine till it gets good and hot??? After I let it cool, it runs fine again for a little while. I have heard about BAP sensors and all, but if it was a sensor, it would not matter if it was hot or not, would it?? I had overheating issue in the beginning, so maybe its a bad ring or gasket? When it gets hot, the problem worsens?? I had the computer reflashed for altitude riding in CO, but this is happening in TX. Thanks for any input. Im totally lost on this

 

IS it completely stock? It could be detonating but I doubt it if its on a stock efi. Did you try adjusting the idle? My Scrambler's idle dropped off after it warms up so I raised the idle some and it straightened out. YOu got me buddy.

 

It is completely stock. When cold, runs perfect. Warms up, runs like junk. I thought about adjusting the idle, but very randomly it will go from idleing at 1170 to idleing at 1600 or more. Then it will dip to 1020. It does this all on its own. Very random. Like I said, Im totally los on it right now, any suggestions is greatly appreciatted.

 

I've seen the same problem noted on this forum before. I had the same problem on my 06 500EFI. It started missing when up to operating temp between 2500 and 3000 RPM. It progressively got worse like you described. Whenever starting from cold it was fine til it warmed up. Since it was so throttle position specific I thought it had something to do with the Throttle Position Sensor which turned out that it was. What I found is that if I pushed up on the wires and plug at the bottom of the sensor the problem disappeared. I put a tie wrap over the top of the sensor and under the plug to snug it up and it runs smoother than it did when new. The plug is hard to get to so I haven't tried to take it apart to diagnose the exact cause of the problem. My guess is that there is a crack or flaw in the TPS that expands as the temps go up causing the problem.
Try fiddling with your plug when it;s having the problem and see if it makes a difference.

 

this might be a longshot but ive herd that some ppl have that same problem when it gets hot..check your fuel level..some have said that when fuel level is low the fuel pump gets hot and doesnt pump right. if thats the case add fuel to submerse and cool pump and it will run fine after that..like i said its a long shot but you never know

 

hi 1867.i was wondering where is the plug on the throttel sensor located?..thx

 

Let me throw this in there also. I live in Texas, I ride a lot in Oklahoma. Once a year I go to Colorado. Last time I went, it ran horrible so I came back and had it reflashed for high altitude. That obviously makes it run richer. Last night I checked my spark plug with only 50 miles on it and it was covered in black carbon. Now Im thinkin: High altitude reflash not very good when your not in high altitude. Now it runs rich in low altitude??? and ruins plugs, doesnt burn all the gas, backfires, sputters like its flooded??? Could this be it???? Please give your 2 cents. Thanks

 

i thought u dont need to do anything to efi's when u change altitude. i thought u only had to do it to carbs.

 

The EFI was only good to 6,000 ft. So Polaris had a reflash to go higher

 

Yeah really, thats was part of the big hooplah, no mre jetting changes to ride in different altitudes.........