okay now this is insane . i put it in about 20 dollars in gas yesterday drove to the other side of town all high way miles . when i got back home i noticed i went from half a tank to almost empty .i did notice i had a check engine light on . so i went to the auto parts for a free check engine light diagnosis . the code reader said that the o2 sensor were at fault . can this be the only problem ? i notice it has a rough idle also . any info would help . i just got this car . like it a lot . thanks again . if you guys need the codes let me know .
okay this is the point i'm trying to get across. i drove from my house to a mechanic shop that was exactly 23 miles away . meaning 23 miles to the location and 23 miles back home . i am now practically on EMPTY . it's this considered the kind of mpg i'll be getting on this cts normally .it's a 3.2
OK, this is the point I'm trying to get across: you haven't calculated a fuel mileage, thus there's no way to judge whether it's good or bad or perfectly normal. You don't know how much fuel you used during that 46 mile trip. If you search this forum (which I'm sure you did, as a new owner) you'll find a number of threads about the inaccuracy of the fuel level gauge, and in particular that there's a lot more fuel from FULL to 1/2 than there is from 1/2 to E.
If you want to calculate fuel mileage, you need to fill the tank, run it to near empty, and refill it so you know how much fuel was actually used.
O2 sensors can affect fuel economy if they are used to adjust fuel/air mixture. You'd probably have other symptoms, too. Rough idle is common if the car is running too rich.
You should get under and check the connection at the O2 sensors and if the connections look good pull the sensors and replace them.
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rough estimate of fuel (assuming an 18 gallon tank?) 46 miles / 6 gallons (half of an 18 gallon tank is 9, but you didn't say you're on empty yet, just close to it.) would net you about 7.5 MPG. That's awful. my 05 with a 3.6 L gets 18-20 city and 25+ highway.
Ouch. With usage like that, I'd be sure to check for an actual fuel leak too, if only to rule out anything dangerous. By brother's Caddy suffered a sudden drop in mileage akin to this one and we found a pinhole leak in his fuel line near the fuel pump. :bomb: Might want to do a quick check to make sure your air intake / filter isn't all blocked up.
And alas, it's only too true. The only dipstick associated with our transmissions is the guy who thought it was a good idea to design such an expensive assembly without one...
ummm i just replaced the air filter .there's nothing wrong there .I also cleaned up the throttle body as it was in real dirty shape.now it idles much smoother.i still have yet to do the fuel filter, oil change, spark plugs . i'm pretty sure then i'll see a significant difference in fuel economy.I hardly doubt i have a leak on a fuel line.You have to keep in mind.I also buck on it.On the highway i do no less then 80 and i put the pedal to the floor at a green light lol.i'll definitely update y'all over the weekend.
The fuel tank has 2 fuel sending units due to its saddle bag shape, the 03's are very common for this going bad. This will cause the gauge to drop drastically when below half full...
When you say you're almost "empty" are you going off of the gauge or did you actually determine this by filling it up again with an entire tank of gas?
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