2006 4x4 volunteer runs slow, barely goes uphill.

[Saint]

Hi. I have a 2006 volunteer 4x4 camo. Over the last year it has been progressively losing power and now is at the point it will barely go up hill. I mean it goes up hill at walking speed. White smoke can be seen from the exhaust too. Runs well flat ground or downhill, but still feels like it's at 50% power. Engine starts fine. Nothing seems really wrong with the motor (no noises or extra noise). Once in a while it will stall if it is in idle for a few minutes. Doesnt seem to have any major issues besides the huge power loss. I'm not smart with mechanic stuff so I don't even know what it could possibly be, but i could probably fix it with instruction if i knew what was wrong. I checked every where online to troubleshoot and no one has this problem. I feel like if I don't fix it now it will die soon or not go up hill at all and be useless on the farm. Please help. 

[kenfain]

White smoke coming from the exhaust is almost certainly water. Which leads me to think you might have a head gasket failure. Have you needed to add coolant? 

[Al-WI]

Diesel or gas engine?

[Al-WI]

If it has engine I had a similar problem a while back. Pulled okay on level but no power up hill and smoked under power. One of the plugs was badly fouled.  Replaced plugs and it ran better but still ‘stumbled’ a lot. Found the plugs fouling again from too rich a mixture. I removed the air cleaner cover and found a mouse nest around the air filter. Cleaned it out, replaced the air filter and it’s running fine again. My suggestion, try new plugs and air filter.

[Al-WI]

I meant “If it has gas engine”