awful mpgs

**emotionalpiracy** · 01-17-2008, 08:52 AM

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?

**180ls1** · 01-17-2008, 02:36 PM

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?

**Frost** · 01-17-2008, 09:17 PM

almost certainly O2s; they control almost all of your cruise fueling. They should be changed at a minimum of 40k miles anyhow.

**98formy** · 01-18-2008, 05:23 AM

Originally Posted by emotionalpiracy

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?

I have an a4 and I wish I could get 400 miles to a tank. I am lucky if I get 225 to a tank driving it nice, then again, I am not stock either.

**Firebirdjones** · 01-18-2008, 06:08 AM

Frost is correct,,,,02's are considered "tune up" items and should be replaced at regular intervals.

They do get lazy over time,,,

**JoshieDoom** · 01-18-2008, 10:58 PM

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???

**35thAnniZ28** · 01-18-2008, 11:20 PM

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

**JoshieDoom** · 01-18-2008, 11:47 PM

Cool. Would a faulty EGR system rape gas?? if so.. its gone ASAP..

**35thAnniZ28** · 01-18-2008, 11:57 PM

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

**JoshieDoom** · 01-19-2008, 12:01 AM

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..

**Firebirdjones** · 01-19-2008, 04:35 AM

Originally Posted by JoshieDoom

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..

A 1/4 mile??? I wouldn't even bother starting the car for that,,,,I'd be footin' that,,,,or at the very most ride a bike. sheeesh.

**Banshee1967** · 01-19-2008, 06:04 AM

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

**Frost** · 01-19-2008, 06:14 AM

Originally Posted by JoshieDoom

Cool. Would a faulty EGR system rape gas?? if so.. its gone ASAP..

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.

**emotionalpiracy** · 01-20-2008, 01:29 AM

id buy em off you but itll only cost me 106 to get them replaced without me having to do any work

**Banshee1967** · 01-20-2008, 01:35 AM

$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.

**Firebirdjones** · 01-20-2008, 05:20 AM

Originally Posted by emotionalpiracy

id buy em off you but itll only cost me 106 to get them replaced without me having to do any work

You replaced them already???? Man thats quick, you just posted this thread on the 17th,,,,you're quicker than I am,,,maybe I'm getting old,,,lol.

**JoshieDoom** · 01-20-2008, 12:31 PM

If you have ever walked a 1/4 mile in kentucky 8 degree winter weather in the woods your pretty frikin awesome

**emotionalpiracy** · 01-20-2008, 12:42 PM

warranty at the place i bought it has a $100 deductible
anything not covered in warranty i do with my friends.

**blue02Z** · 01-20-2008, 01:15 PM

Originally Posted by emotionalpiracy

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?

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

**Bottesini** · 01-20-2008, 01:25 PM

Originally Posted by blue02Z

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

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