Bad gas mileage
#1
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Bad gas mileage
I have a 95 SC SSE1. I have Delco Plat plugs, new O.E. wires, semi synth oil. I keep vehicle in performance mode and I have played with octane ranging from 87-94 but cant seem to get more that 13mpg out of tank. My tank is 18gal i usually run out at abt 230miles. Could this be normal. I usually drive about 80mph. I have no special exhaust system, I have gone to a 180 t-stat. K&N filter and recently took the front portion off of my airbox so its just a big hole. Never done O2 sensor, although my CE light comes on after about 10min of driving and stays on till i restart. The last time it was checked it came up as code 640 QDM. Please help!
#2
Hey, welcome to the club. I got the same year and trim line that you do.
As far as gas mileage, my guess would be O2 sensors. I am pretty sure mine need to be replaced and my gas mileage is roughly the same as yours. I know if I keep it to 60 and highway speeds I can get up to 400+ miles from a tank, but I tend to give it alot of gas requently which I know will hurt my mileage, but it'* SC'd, so who cares!
So what it the cars mileage now? If my memory serves me right, O2'* usually need to be changed ever 60k - 70k miles.
CE light? I'm probably just haveing a menatl lapse but which light is the CE light?
As far as gas mileage, my guess would be O2 sensors. I am pretty sure mine need to be replaced and my gas mileage is roughly the same as yours. I know if I keep it to 60 and highway speeds I can get up to 400+ miles from a tank, but I tend to give it alot of gas requently which I know will hurt my mileage, but it'* SC'd, so who cares!
So what it the cars mileage now? If my memory serves me right, O2'* usually need to be changed ever 60k - 70k miles.
CE light? I'm probably just haveing a menatl lapse but which light is the CE light?
#4
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Don't ever run below 91 octane in a SC bonneville....bad news. I don't have my book handy right now, so I can't tell you what that code is, but a couple months ago, my mileage too about an 8mpg nosedive. I changed the O2 sensor and it came right back up. Sucker had me running richer than snot from a 4 year old.
I'd check the code first (I can look this up in the morning), and then maybe think about O2'*.
I'd check the code first (I can look this up in the morning), and then maybe think about O2'*.
#5
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Re: Bad gas mileage
Originally Posted by G2SSEi95
I have a 95 SC SSE1. I have Delco Plat plugs, new O.E. wires, semi synth oil. I keep vehicle in performance mode and I have played with octane ranging from 87-94 but cant seem to get more that 13mpg out of tank. My tank is 18gal i usually run out at abt 230miles. Could this be normal. I usually drive about 80mph. I have no special exhaust system, I have gone to a 180 t-stat. K&N filter and recently took the front portion off of my airbox so its just a big hole. Never done O2 sensor, although my CE light comes on after about 10min of driving and stays on till i restart. The last time it was checked it came up as code 640 QDM. Please help!
#6
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I would go for the whole 9 yards . O2 , pcv and the EGR valve , How long since your last plug change ? Might wanna get the injectors clean too! See ya at work!!!
#7
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bad gas mileage
Whats a PCM? Is that the same as a ECM Electronic Control Module? I purchased the car in DEC 2001 at 58,500miles. I have 74,500 now. I rexcently took care of the PCV and at AC Delco platinum plugs have about 7000,00 miles on them. I tried to get a O2 sensor at Pep Boys, AutoZone, and Strauss, but they all carry BOSCH. I know u guys told me to stay away from Bosch O2, right?
#8
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Re: bad gas mileage
Originally Posted by G2SSEi95
Whats a PCM? Is that the same as a ECM Electronic Control Module? I purchased the car in DEC 2001 at 58,500miles. I have 74,500 now. I rexcently took care of the PCV and at AC Delco platinum plugs have about 7000,00 miles on them. I tried to get a O2 sensor at Pep Boys, AutoZone, and Strauss, but they all carry BOSCH. I know u guys told me to stay away from Bosch O2, right?
HOWEVER....if you have a PCM problem, I wouldn't mess with the O2 yet. Kinda like putting out the match before the forest fire.