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Discussion Starter #1
My 625I has this problem: When its cool or cold outside it runs great. But now that it is warm or hot outside it idles and runs rough. It started at the end o summer last year. once it got cold outside it began running great all winter. Now that its getting hot outside it started back running rough again. checked all connections and the fuel system. But still looking.
 

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Discussion Starter #3
Filter

I put a new one in but did not try it without the filter. I will though.
 

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cooler air is more condensed which may indicate the engine may be starving for air once the weather warms up, I'm not familiar with your vehicle so hopefully there may be some air/gas adjustments you can make. As for removing the air filter to see if that helps, remember, it supposed to have an air filter so if removing a clean air filter helps at all, it will at least point you to an air issue.
 

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Most engines run better in a cooler dense climate..Sounds to me you might be running a Tad lean..Change your fuel filter, pull the boot of the throttlebody and clean it with carb clean..do a t-body service, clean the throttle blade..I change my fuel and air filters once a year..I also run Super for the gas,,,Chevron has the best fuel additives for cleaner injectors..As far as the airfilter goes, I bought the 1 for a 850d because it has an inner filter for better cleaning..this way I have no dust getting into my Motor
 

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I suspect the opposite. Cold, dry winter air is more dense. Hot, humid summer air is less dense causing the engine to run rich. Removing the air filter allows the engine to breathe slightly freer and slightly leans the mixture. If the engine runs better with the air filter removed it makes me think the filter was dirty in the first place or that maybe something like an oxygen sensor is heading south.
 

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Actually if the filter was plugged it would run rich..Hot dry air,, all 4 cycle motors will tend to be lean...as far as the 02 sensor, if it were to fail the check engine light will be on...Not to be a jerk on this forum ...But all 4 cycle motors will run with the most H.P. at a cooler climate tending to be Stoichiometric 14.7...if all the parts are in good working order...if it was turbocharged everything changes...Stoich is 12.0
 

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Discussion Starter #8
Hot v cold

Well, we took the filter off with no change. No check engine light. It idles rough and runs rough no matter what speed. I still think its a sensor problem.
 

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if the coolant level was low, or the ECT was not reading correctly,,or if the MAP was not working correctly..you can have run Problems...You can try a sparkplug on the end of the wire and see if its a good spark,,..How old is this Gator?
 

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Discussion Starter #10
It's a 2013 model. It's only got 246 hours on it. We have put a new air and fuel filter on. A new set of spark plugs. It runs perfect on a cool day.
 

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Also another thing to consider is your altitude where you ride this Gator..along with heat of the summer, ethanol in regular unleaded gasoline tends to Boil faster, making a rig go lean, thus having a Lean Misfire..Altitude will intensify the situation...This is the reason why I run Super from Chevron gas
 

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so, great discussion. most of the theories are leaning toward not enough air causing it to run rough. dane brings up the possibility of it being too rich. But Fred, my man, throws out the term stoichiometric which basically supports that the fuel is a constant and air becomes the variable. As mentioned before, I'm not familiar with your model, gas or diesel? carb or injection?
 

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But fuel is not a Constant, air and fuel can be a Variable..Air will be a lot less, where fuel is a Common Problem, a big problem...Heat can be a big Issue.. compression ratio and so on,,If you combine Altitude with Heat,,/summer. compression ratio.. cheap Gas, a lean misfire can be an Issue..cant see the Rig/ or rub my crystal bald Head!! but would leave me to believe this is a Common issue with Altitude.and a not very efficient Computer to run a Computerized toy....This is an open forum...You don't see Planes falling from the Sky Much...They run on Avgas...111 Low Lead...That is what it is across America...Its a Constant...............Don't get me Started!!!
 

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I knew I should have looked up stoichiometric instead of relying on my failing memory. But as you mention planes don't "generally" fall from the sky and the gator being more of a toy how much difference will the altitude make, assuming W5kgt isn't running the tops of the Himalayas. I bought a quad in Phoenix with the altitude in the neighborhood or 1000' and took it up to chino valley, alt a little over 4K' and found no difference in its performance. I understand you have a much greater understanding of how fuel can improve a vehicles performance but doesn't the average ATV/gator have a much wider range for crappy gas and air restrictions without resulting in poor performance? And by the way, why are we more interested in the root cause? Where's Wfkgt to give up the all important question of his altitude?
Fred, relax when giving us great professional insight, we appreciate it. Most of the folks here are just trying to enjoy their toys. So, don't get me started!!!:)
 

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Elevation can make a difference on a High compression motor running cheap regular with ethanol mix..Different States have different amounts added..A very common Problem in Oregon is high performance rigs/Lexus,,acuras and so on tend to Ping with regular unleaded...Pre-ignition is bad..puts little holes on the top of pistons..So I guess my point is with running Higher Octane fuel , with the heat of summer and some elevation it can be a Problem in some Rigs...I do not know the Compression Ratio in his rig......Its a Safe bet to run Super in all gas toys..Reallisticily..with better performing Fuels you will get more optimum power and Better fuel Mileage..I get an average of 90 miles to 5 Gal. of super in my Gator and I am loaded to the hilt when I go out...Sorry about the don't get me started thing...Just a saying I have
 

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no need to apologize, I've read quite a few of your posts and always appreciate someone sharing their knowledge, even if it is from a "bald guy" :) Your words, not mine. Now, if we could get the guy to try some better fuel and give some feedback it would be great to find the answer to help anyone else who has the same problem. And I'm going to try the better fuel in my quad this year, I only go through around 5 gallons a summer and can afford the extra $1.25
 

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...They run on Avgas...111 Low Lead...
There has ever been a 111 low lead. The most common aviation gasoline by far is 100LL and it's blue in color. Currently $5.80 a gallon so be glad you don't run it in your gator.
 

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So it Maybe 110 low lead,,,I thought it was 111 low Lead...and yes its blue in Color,,and you would Have to Be a Dumbass to run it youre Gator....Sorry Dudane your an Idiot....You don't have a Clue as to what you are Talking About
 

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I'm sure we've all made some typo's and didn't completely clarify our thoughts when attempting to help others with questions/problems. Just my opinion and not in any particular order or preference but due to the resent posts, Fred, dane, xcopterdoc and deeresales101, and anyone I may have left out, all have given very helpful advice to help those that are less "experienced" than you guys are and I've learned ALOT with your help. So, I'm still interested in what the actual cause is for the rough idle in warmer weather. But I will agree, jet fuel in a gator may be a little too much. I've got 5 acres and have no problem taking a minute or so to cover the ground from point to point:D
 

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The 625i has had some issues with running rough. Mostly due to faulty throttle position sensors or someone messing with them and having the baseline set up wrong. Also up under the under seat plastic panel is a small inline fuel filter, white, about the same size as a cig butt. Seen many problems caused by this. Stick to the basics to determine what the root cause is. Fuel, unless just pure rotten, is not likely an issue.
Ya'll play nice now!
As a side note to all who burn Gas as a fuel.. your #1 diagnostic tool is a spark tester and pulling spark plugs and looking at them. You can tell ALOT by the color of the plug.
 
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