Help really bad gas mileage
Registered User
Joined: Jan 2010
Posts: 106
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From: Florida
The owners manual has recommendations for shift points to achieve good gas milage. They are like impossible to hit tho. First to second is recommended at 8mph and 5th-6th is at like 35mph. How is that possible? I shift first at like 20mph and second at like 45mph
You have a fuel leak somewhere is my guess. Do a sniffer test. You could also get your A/F ratio's checked. The only other possibility is that your O2 sensors are sending WAY more fuel than it should be.
if you have a leak you can get a fault for EVAP
if your o2 is bad you should get a fault for that.
if there are theifs you should get a gun.
either way hit up autozone first and get the codes checked first then hit up the dealership.
if you can do something for free, do that first before spending the money. If you been driving like this for a while its not like your in a hurry to get it fixed so you can spend some time figuring it out... people who only get 100miles will notice ASAP.
if your o2 is bad you should get a fault for that.
if there are theifs you should get a gun.
either way hit up autozone first and get the codes checked first then hit up the dealership.
if you can do something for free, do that first before spending the money. If you been driving like this for a while its not like your in a hurry to get it fixed so you can spend some time figuring it out... people who only get 100miles will notice ASAP.
Thanks for all the advice fellas. I am was thinking O2 sensors. I am pretty sure that my gas gauge is working fine, when I full up its about $50 every time but I will keep an eye out for that. My car is basically back to stock only aftermarket stuff on it is my stillen cold air, plenum spacer, coupe 19's, and grounding wires. This has only been happening for maybe a month, the car only drives about 5-8 miles a day on average. I called my friend at pep boys and he said if no light is on the dash he can't check it for codes that I would have to take it to the dealer. Even when I uses to beat on the car locally and highway combined I would get 225-250 and still have 1/4 tank left. Will be trying the ecu reset today. I will be going down to the dealer this week.
Any update on this? My guess would definitely be a Vacuum leak. Possibly the FPR... you could just be DUMPING fuel into the cylinders this way... something is definitely WAY wrong tho... because I get 22-24 mpg out of my 03.5 with 152k on it 
i wish i saw this earlier and told you NOT to reset the ECU
One thing you do clear is the long term fuel trims that is stored in the ECU. Tech normally look at that to see how the end is actually running.
Sadly since its done already, you might not get a straight answer, only thing to do is drive it normally for another 2-3 weeks and then take it back. Yea i know at 100miles a tank that is going to be a VERY costly 3 weeks.
I guess you can just take it in and see whats up.
For future reference, this whole resetting of the ECU is somewhat pointless. The $100 sensor that is in charge of reading the value really does a good job. I never reset the ECU for anything. People on forums do it and make bold claims but they are a placebo effect, 90% of the time. People refer to it as the DYNO BUTT.
Please do post up their findings, as i think its more like a vac leak by a broken hose or loose hose, But i have a feeling they are not going to be able to find anything.
One thing you do clear is the long term fuel trims that is stored in the ECU. Tech normally look at that to see how the end is actually running.
Sadly since its done already, you might not get a straight answer, only thing to do is drive it normally for another 2-3 weeks and then take it back. Yea i know at 100miles a tank that is going to be a VERY costly 3 weeks.
I guess you can just take it in and see whats up.
For future reference, this whole resetting of the ECU is somewhat pointless. The $100 sensor that is in charge of reading the value really does a good job. I never reset the ECU for anything. People on forums do it and make bold claims but they are a placebo effect, 90% of the time. People refer to it as the DYNO BUTT.
Please do post up their findings, as i think its more like a vac leak by a broken hose or loose hose, But i have a feeling they are not going to be able to find anything.
Ok fellas time for an update. Since I did the ecu flash ( about 2 weeks ago) I have been getting better fuel milage right now 146 and I'm at half tank. Went to the dealer and they couldn't find anything. The AFR is within specs, the tech told me drive with it for a while and next time it starts to happen don't reset the ecu just bring it in may the ecu can tell them something else. Other than that their is nothing wrong with the car. Plugs and wires are good, oil, and tranny. So I will have to see as time goes on.
