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As the title says, the character of my car changes depending on the temperature outside. When it is in the 90s it seems to accelerate a little slower, shift a bit roughly and idle rougher as well.

On days like today, however when its ~75 out, it runs like a dream.

I'll have the ac on in both instances, so i don't think that has anything to do with it... Is this anything I should be concerned about?

I don't know terribly much about the actual mechanics of a car, but now that I have a vehicle to be proud of, I am trying to learn.
 

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Air density is different between hot and cold (more dense when cold). Therefore your achieving better volumetric efficiency when its cold (more dense air in the cyclinders mean more oxygen molecules to aid combustion). Also, the air inlet temperature sensor will retard the timing to prevent knock when ambient temperatures are high as well. Retarded timing hurts bottom end.
 

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2003 540i - M Sport
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the colder/denser the air outside the better your car will perform....just like easyover mentioned above. simple physics :)

go out on a nice drive when its 50 degrees outside....(usually at nite)

you'll see how well the car runs....
 

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just havin a heart attack
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I noticed the same thing with my 98.
 

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get someone to check your exhaust camshaft sensor, it may have to be replaced

good luck
 

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Temperature and barometeric pressure both affect the performance.

Ideal is cold day with a high pressure system in the area where you live. If you pay attention to both of these numbers and the performance of your car you will easily be able to feel the difference.
 

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Temperature and barometeric pressure both affect the performance.

Ideal is cold day with a high pressure system in the area where you live. If you pay attention to both of these numbers and the performance of your car you will easily be able to feel the difference.
That describes a Track Record day in racing.
 

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Also gasoline actually expands when it is hot out, so you don't get the same amount of gas you suppose to get. I Canada, gas station requires to cool the pump at a certain temperature so that consumers don't get screwed.
 

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Dont for get colder denser fuel make your car run better,16valex is right,alot of gas gets trucked to your servo warm,then becuase there's less in the tanks underground the servo pass the it on to you in high prices because there less in than when the trucked pumped it,

temperature and barometric pressure both affect the performance.

Ideal is cold day with a high pressure system in the area where you live. If you pay attention to both of these numbers and the performance of your car you will easily be able to feel the difference.
Spot on,we've been getting these alot,some times i think my car isn't turned it's that smooth at idle when it's warmed up lol.
 
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