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Thread: awful mpgs
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01-17-2008, 08:52 AM #1
- Join Date
- Oct 2007
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- Union Beach, NJ
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- 145
triple black- 02 z28 m6
awful mpgs
my car has less than 50,000 miles, and for some reason im getting on average less than 250 miles per tank. normally i can get over 400. how often do spark plugs go bad on ls1s? would running lean cause mpg issues?
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01-17-2008, 02:36 PM #2
check your o2's, maf, and plugs/wires. but your plugs should be good you never know when they will go same with your o2's and maf. lean should not ccause that problem running rich should. didi you get any codes or did you change anything around with your car?
1998 Firebird Formula WS6... few things done.
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01-17-2008, 09:17 PM #3
almost certainly O2s; they control almost all of your cruise fueling. They should be changed at a minimum of 40k miles anyhow.
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01-18-2008, 05:23 AM #4
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01-18-2008, 06:08 AM #5
Frost is correct,,,,02's are considered "tune up" items and should be replaced at regular intervals.
They do get lazy over time,,,
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01-18-2008, 10:58 PM #6
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- Oct 2007
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- Beaver Dam KY
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- 7,745
79 T/A -91 Firebird- 1998 Trans Am -Oynx Black
Ive get horrible gas mileage as well... my rear 02's are gone(cats) and my egr code is on..... so im gonna get rid of the AIR and EGR system.. and change the 02 sensors......... which brand is the best guys???
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01-18-2008, 11:20 PM #7
i got some ntk's from summit which came out to 110 altogether i think..their smaller and fit alot better with the headers i got
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01-18-2008, 11:47 PM #8
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- Oct 2007
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- Beaver Dam KY
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- 7,745
79 T/A -91 Firebird- 1998 Trans Am -Oynx Black
Cool. Would a faulty EGR system rape gas?? if so.. its gone ASAP..
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01-18-2008, 11:57 PM #9
i heard removing the egr system wouldnt affect it..but not sure..wait until frost signs on..he's an expert on the ls1 computer
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01-19-2008, 12:01 AM #10
- Join Date
- Oct 2007
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- Beaver Dam KY
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- 7,745
79 T/A -91 Firebird- 1998 Trans Am -Oynx Black
My car is daily driver and i have to drive 1/4 mile to work each way.. so im not really worried to much about extreme power adding, Just something i can kill ponies and ricers on the weekends. My EGR is out and i thought I would clean up everything and kill emissions all together..
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01-19-2008, 04:35 AM #11
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01-19-2008, 06:04 AM #12
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- Aug 2006
- Location
- Michigan
- Age
- 53
- Posts
- 178
Black- 98 T/A
I just went through the SAME thing two weeks ago..Check out my posts on it. PCM showed no codes, mileage dropped from 350 to 200-225 a tank.
Spent $400 on new irridiums, wires, feil filter, air check valves..etc. Still no change in mileage.
Changed both o2's, mileage was fine.
I have an extra set of AC Delco O2's if you are looking.
http://www.ls1.com/forums/showthread.php?t=74610
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01-19-2008, 06:14 AM #13
Nah...
The reason to almost always suspect O2s is like I said, they control almost all fueling of the car. The areas they do NOT control include startup and a few seconds after that (more than a few seconds if cold), and WOT. So, if your car is not in one of those 2 areas, the O2s are updating the mixture continuously. The other rub of them is that they don't usually fail outright, they usually get lazy and out of range. so you think they are still good.
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01-20-2008, 01:29 AM #14
- Join Date
- Oct 2007
- Location
- Union Beach, NJ
- Posts
- 145
triple black- 02 z28 m6
id buy em off you but itll only cost me 106 to get them replaced without me having to do any work
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01-20-2008, 01:35 AM #15
- Join Date
- Aug 2006
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- Michigan
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- 53
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- 178
Black- 98 T/A
$106 for two new O2 sensors? Even with employee discount through friends at NAPA and Autozone, cheapest I could get was $63.99 and that was Bosch. Internet search was the same price.
Disbelief...
You should learn how to work on your car. Sensors take maybe 10 minutes to change out and it is real easy. A real good project to start.....OK, I'll shut up.
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01-20-2008, 05:20 AM #16
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01-20-2008, 12:31 PM #17
- Join Date
- Oct 2007
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- Beaver Dam KY
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- 7,745
79 T/A -91 Firebird- 1998 Trans Am -Oynx Black
If you have ever walked a 1/4 mile in kentucky 8 degree winter weather in the woods your pretty frikin awesome
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01-20-2008, 12:42 PM #18
- Join Date
- Oct 2007
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- Union Beach, NJ
- Posts
- 145
triple black- 02 z28 m6
warranty at the place i bought it has a $100 deductible
anything not covered in warranty i do with my friends.
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01-20-2008, 01:15 PM #19
400 miles to a tank?!?!?!? OMG! if i drive normally i get around 225 a tank. EVERYTHING on my car is up-to-date except the o2's. i didnt know they needed to be replaced like that. i need to get new ones, i have 75k.
sorry for the hijack, but hey Frost, i pulled the fuse on my AIR pump it thru the Check engine code which i knew it would. but what will it do if i drive it with the light on? thanks
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01-20-2008, 01:25 PM #20
- Join Date
- Sep 2007
- Location
- Denton, Texas soon Lafayette, Louisiana
- Posts
- 2,956
Blue- 2002 Z28 Camaro M6
If you are close to stock getting over 300 a tank on an 02 should be pretty easy (bigger tank in the 02). If the SES light is just from the AIR pump you should not have any problems other then getting annoyed from the light. I know I had mine running for a while when I was running with no cats, for a while I kept freaking out when I looked down and saw the light on, but that was purely from instinct. The red from the odometer still catchs me off guard sometimes
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