Excessive Fuel Consumption
Thread Starter
Staging Lane
Joined: Jul 2010
Posts: 69
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Ok, today I installed the new Denso upstreams and I am at a 1/2 tank. I am going to fill up and c how it goes. I do notice that when the link shuts off, the gauge does not read full, EVER. No matter how long I wait. It certainly does not read over full.
Do you have aftermarket gauge faces?
Thread Starter
Staging Lane
Joined: Jul 2010
Posts: 69
Likes: 0
No I dont, but I did have the pointers off at one point. I thought about that, but if it was the pointer position, then the amount of gas being used would be off as well and the last time I posted about the amount of gas used, I used 10.9gal and the pointer was at 1/8 tank. The manual says the tank is 16.8gal. That gives approx. 4.2gal per 1/4tank. 1/4 tank would mean I used 12.6gal. Wait a minute. My check gauges light came on and it took only 12.5gal. That means it let's u have 4.3gal to get to a station? Is that right? When the light comes on, how much gas should I be able to put in the tank? I went immediately to the station. Maybe the needle is off?
Thread Starter
Staging Lane
Joined: Jul 2010
Posts: 69
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WTF!!!!! How can a gas gauge read different depending on the wag the car sits WHEN ITS FULL!!!!!!! It kust read over full, now its reading not even full. God I love old cars. I have NEVER had this many issues with my now 44yr old Camaro. I should have stuck with the installing ac plan and saved the money I spent on this.
Thread Starter
Staging Lane
Joined: Jul 2010
Posts: 69
Likes: 0
I just pulled the connector for the sending unit and with a full tank, the ibm reading is 224ohms. My understanding is, full=240ohms and empty=40ohms. I know for a fact the tank is full. Well, the pump shut off and it would only allow me to put in about $.10 more. That's all. Any ideas?
The float that senses the "fullness" of the tank is non linear. So, the half way mark is really not half way. Its a little less than half a tank. You'll notice that the top half of the gauge moves slower than the bottom half. Getting around this on a modern car requires some computing power but most cars just have a simple float system. Back in the day, when gas tanks were symmetrical - it was easier to measure the tank with a float. Now that they are blown plastic and an odd shape its a totally different ball game.
So... that's why you have to ignore the gauge when calculating mileage. You have to read what's on the pump.
And... it doesn't really matter where the needle is because it really doesn't tell you much. I'd suggest filling it up and then moving the needle to the position you want it to read when full and make sure its where you want it when the fuel light comes on. (My stock car read just over the "F" when full before I pulled the needles off the first time.)
So... that's why you have to ignore the gauge when calculating mileage. You have to read what's on the pump.
And... it doesn't really matter where the needle is because it really doesn't tell you much. I'd suggest filling it up and then moving the needle to the position you want it to read when full and make sure its where you want it when the fuel light comes on. (My stock car read just over the "F" when full before I pulled the needles off the first time.)
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Staging Lane
Joined: Jul 2010
Posts: 69
Likes: 0
The float that senses the "fullness" of the tank is non linear. So, the half way mark is really not half way. Its a little less than half a tank. You'll notice that the top half of the gauge moves slower than the bottom half. Getting around this on a modern car requires some computing power but most cars just have a simple float system. Back in the day, when gas tanks were symmetrical - it was easier to measure the tank with a float. Now that they are blown plastic and an odd shape its a totally different ball game.
So... that's why you have to ignore the gauge when calculating mileage. You have to read what's on the pump.
And... it doesn't really matter where the needle is because it really doesn't tell you much. I'd suggest filling it up and then moving the needle to the position you want it to read when full and make sure its where you want it when the fuel light comes on. (My stock car read just over the "F" when full before I pulled the needles off the first time.)
So... that's why you have to ignore the gauge when calculating mileage. You have to read what's on the pump.
And... it doesn't really matter where the needle is because it really doesn't tell you much. I'd suggest filling it up and then moving the needle to the position you want it to read when full and make sure its where you want it when the fuel light comes on. (My stock car read just over the "F" when full before I pulled the needles off the first time.)
Thread Starter
Staging Lane
Joined: Jul 2010
Posts: 69
Likes: 0
What actuallu controls the check gauges light in reference to the feel gauge? In other words, is there a sensor that mounts to the tank, does the pcm read the position of the sending unit or is it something else? For example, if the light cones on because the gauge is in the red, if u reposition the needle to say 1/4 tank(just for example), will the light go out? What actually makes the light turn on?
Thread Starter
Staging Lane
Joined: Jul 2010
Posts: 69
Likes: 0
i wanted to give an update on the situation. after initially changing the upstream oxygen sensors i did not notice any difference, but now it seems to be picking up mileage. I just got gas before the light came on and it took 11.5gal and the odometer read 230 miles. that's equals 20mpg. I guess as the new upstreams continue to relay info it will get a little more. help, even the gas gauge is reading over full on the highway and it has NEVER done that. I did add a bottle of chevron with techron so maybe that is helping as well. i appreciate everybody helping out and i will.!
I was getting 24 mpg and found one of my downstream O2 sensors was bad. I just replaced them along with my spark plugs & wires (I'm getting close to 100K miles.) and I'm back up to 28 mpg on the highway.
Thread Starter
Staging Lane
Joined: Jul 2010
Posts: 69
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This was going to be my next step. I already changed the upstreams. I had a guy ride with ne yesterday while watching the tune. He said it has room for improvement. Both in performance ans economy. It costs $400 for a street tune. As soon as I get the money I'm going to get that done as well.
Thread Starter
Staging Lane
Joined: Jul 2010
Posts: 69
Likes: 0
Ok heres the latest. It's been a week and 2 tanks of gas and 2 bottles of Chevron Techron. The last tank of gas netted me 276.7 miles. Also, I noticed the immediately after filling up the needle would read over full and would stay there, but ONLY for the 1st 20-30 miles OF HIGHWAY DRIVING. With highway driving immediately after filling up, I would think it should stay there for much longer than 20-30 miles, buy that's it. I still have not changed the downstreams, but I am going to. The gauge still varries its reading depending on which way the car is pointing in my driveway. What do the experts have to say???
