every morning i start my car and let it warm up for about 10 minutes then i start to drive it. I could have a quarter tank of gas and by the time i drive maybe 15 miles i would have about an eighth of a tank left. Is it normal for our cars to run rich in the morning, if so is their anything to do about it

 

mine doesnt really do that. you're in ohio though isnt there a bad snow storm or something goin on right now?

 

yea but its not just in the winter, its all year round, it burns gas pretty bad for the first 15 miles then its normal the rest of the day

 

i believe every car runs a little richer in colder weather. Idling for 10 minutes shouldn't go through much gas at all, but the colder it is and the longer it takes to warm up the oil, then the more gas you probably will be using. Not sure about 1/8th tank worth, but i don't think gas gauges are extremely accurate anyways.

 

They run rich while cold. If you 02 sensor is bad it will also run rich all the time.

You will also notice a loss in mileage with a clogged air filter.

 

02 sensor is in the cat right?

 

There is one before the cat that controls the mixture when the car is warmed up enough.

 

hm how would i go about checking if it was bad or not, like i said maybe its only because its colder out that it runs rich but i drive alot because i deliver pizzas so im constantly stoping and starting and still manage to get about 21.5mpg daily driving but when im easy on it i can get 22

 

when did you last clean/replace your air filter? fuel filter? how many miles?

 

well i got the car in september 07 with 14314 miles on it, now it has 25500 so i havent did any of that but i think the miles are so low that i wouldnt have to or am i wrong

 

You should check the air filer to make sure its not dirty.

 

i noticed that the emptier the tank is, the more innacurate the fuel needle is when you first start te\he car. I think when your on a low tank, that it reads you have more fuel than you really do, and it is slowly adjusted during driving, giving the illusion that you go through gas a lot fatser than you are. Im basing this off the fact that this only happens to me below 1/2 a tank, and the lower it is, the more extreme it is

 

1. The fuel gauge is not incredibly accurate. After I get below 1/2 tank the fuel gauge will bounce around a bit just like yours.

2. Letting the car warm up for 10 minutes is a little excessive. I would say that letting the car warm up for 5 minutes is probably fine. I usually let my car warm up for about 1 or 2 mintues then I just drive really easy until the car warms up.

3. The cars do run rich until the coolant temp gets to about 130 degrees. If one fo the O2 sensors is bad, or if your air filter is clogged it can cause you to get poor gas mileage as well. Typically if the O2 sensor is bad you should get a code. The air filter should probably be changed at least by 25,000 miles. I usually take my K&N out and clean it at about 15,000.

 

I just warm mine up to 100*F every time. That is pleanty.

 

I dont really have a problem with warming it up in the morning, I only do it if its snowing, other than that start and go. Yeah now get this one, I get an average of 21.5 MPG, and I have a permanent lean code on but only when its 40 degrees or below. Its been at the dealer many times trying to fix it, they tried MAF and updated the CPU to newer software, nothing worked. Everyone pretty much gave up on it.

 

Bad 02 sensor. It reads lean so the engine dumps fuel even though it is not actually lean. So now you are SUPER rich and wasting tons of fuel.

I am getting about 20MPG in open loop (currently not running an 02)

 

it may just be the guage itself. with my car, (happened on both of my cobalts) the guage goes down extremely slowly when the tank is full, but as it runs down it goes much faster. my guage was on "E" this morning, fuel light flashing, and i still have about 2 1/2 gallons left.

 

The reason why it seems that ur burning more gas when the needle goes below a half tank is because of the way the tank is shaped.Its wider on the top than it is on the bottom.Think of a gallon of water,when its full it drains slower,once it gets towards the bottom it drains out faster.Your car isnt burning more gas when the level is lower.

 

beat me to it