Could faulty front O2 sensors cause bad gas mileage?

asiansensation78 · November 7th, 2009, 01:32 AM

So update on my original question where I asked why I was getting 11 mpgs. I returned the tune to stock, and gas mileage is still horrid. Spark plugs, fuel filter, air filter, etc. have all been changed within the last 6 months so I'm not going to sweat the little details. Gas mileage dropped after I had my o/r X pipe installed and I remember seriously stretching the front sensors to go into the pipe. This may have damaged them though the car isn't throwing a code.

Would replacing the front O2's be the most obvious solution to solving my gas mileage dilemma?

AndrewA. · November 7th, 2009, 01:45 AM

I thought that the O2 sensors only read the levels..too rich too lean. But i just searched real quick and found an article saying that if they do read wrong due to faulty wires than it will affect your MPG by trying to adjust something that isn't even wrong.

But i never noticed any thing wrong when i went to a o/r x with out my tune?? Maybe sense yours is damaged its just way outa wack?

carnut59 · November 7th, 2009, 03:23 AM

mine sucks because of the gears.

Huxley · November 7th, 2009, 04:27 AM

I was having this same problem. I took it to AMMCO for a Fuel Induction. o_o Well...basically they flushed out my fuel system and pretty much cleaned it new.

ImpOnFire · November 7th, 2009, 11:02 AM

the sensors read the air/fuel ratio, so if theyre bad/reading wrong then they will force the fuel injectors to make the gas leaner/richer depending on how its reading, of course causing the car to not run as well plus causing bad gas mileage

but the O2 sensors are psycho sensitive in the mustangs (atleast the ones ive delt with) so if there was something wrong with them it should have thrown code. id put some injection cleaner in there first and see if that doesnt help first

B0B · November 7th, 2009, 12:25 PM

i would go ahead and replace them. i've never gotten below 16mpg with my car and its heavily modded. you're running super rich from the sounds of it.

ford6693 · November 7th, 2009, 02:40 PM

I remember seriously stretching the front sensors to go into the pipe

do you not have o2 extensions?? if not it might be a seriously good idea to do so. check the harness and check the fuse for the 12v heater wires as well, for if that fuse is blown you might have a short somewhere.

MiddleAgeMustang · November 7th, 2009, 06:45 PM

If I understand them correctly, O2 sensors before the cats are for monitoring A/F ratio. Any O2 Sensors after the cats are just to see if your cats are working. The rear sensors would not be my first place I'd look.

This may seem too obvious,but are you hole-shotting everytime you start out? What do your plugs look like?

asiansensation78 · November 8th, 2009, 04:10 PM

It started getting bad gas mileage after the midpipe was put in. The plugs all look excellent, last time I changed the plugs they had 20,000 miles on them and looked like they were put in last week. I'll check the fuses as ford6693 suggested and go ahead and change the O2 sensors. Should I go ahead and order the extensions too?

Pittbull · November 8th, 2009, 04:27 PM

id def change th eo2 sensors. i had the same problem, im getting 14mpg last time i checked and both my o2 sensors were bad.... i replaced them but have yet to check my mileage

Smoothgrandmama · November 8th, 2009, 04:30 PM

Is could be your front o2 sensors......

Thay can affect mileage

asiansensation78 · November 8th, 2009, 09:17 PM

Ok, fuse is good, so I ordered 2 front O2 sensors, will install as soon as they get in. Do I need extensions as well?

Pittbull · November 9th, 2009, 12:17 AM

Idk about the upstream sensors... They look tricky to get to :/

November 7th, 2009, 01:32 AM	#1
asiansensation78 Regular 02 GT Vert 15:43.28@25.21 Too many naked bitches in the back Join Date: Jul 2009 Location: Miami Posts: 202	Could faulty front O2 sensors cause bad gas mileage? So update on my original question where I asked why I was getting 11 mpgs. I returned the tune to stock, and gas mileage is still horrid. Spark plugs, fuel filter, air filter, etc. have all been changed within the last 6 months so I'm not going to sweat the little details. Gas mileage dropped after I had my o/r X pipe installed and I remember seriously stretching the front sensors to go into the pipe. This may have damaged them though the car isn't throwing a code. Would replacing the front O2's be the most obvious solution to solving my gas mileage dilemma? __________________ Going in as soon as I find a jacked bald guy to sit in my car to tell me I'm granny shiftin' and not double clutchin' like I should Don't want your 75 shot jets anymore? PM me and I'll buy them. Size 40 & 26

November 7th, 2009, 01:45 AM	#2
AndrewA. Hardcore Enthusiast 2001 Mustang GT 8.9@78 Join Date: Jul 2007 Location: DFW Texas Posts: 1,384	I thought that the O2 sensors only read the levels..too rich too lean. But i just searched real quick and found an article saying that if they do read wrong due to faulty wires than it will affect your MPG by trying to adjust something that isn't even wrong. But i never noticed any thing wrong when i went to a o/r x with out my tune?? Maybe sense yours is damaged its just way outa wack? __________________ Fire it up, burn it down.

November 7th, 2009, 03:23 AM	#3
carnut59 Enthusiast 2001 mustang gt two days slower than a toyota prius Join Date: Sep 2007 Location: dfw, texas Posts: 539	mine sucks because of the gears. __________________

November 7th, 2009, 11:02 AM	#5
ImpOnFire Newbie 99 failboat 10 min @ 1/4 Join Date: Nov 2009 Location: 33.04, -80.14 Posts: 13	the sensors read the air/fuel ratio, so if theyre bad/reading wrong then they will force the fuel injectors to make the gas leaner/richer depending on how its reading, of course causing the car to not run as well plus causing bad gas mileage but the O2 sensors are psycho sensitive in the mustangs (atleast the ones ive delt with) so if there was something wrong with them it should have thrown code. id put some injection cleaner in there first and see if that doesnt help first __________________ Your anguish sustains me

November 7th, 2009, 12:25 PM	#6
B0B Boost gets you laid 2001 Mustang GT 12.93@113.7 (on the 18's) Join Date: Dec 2006 Location: Milton, WA Posts: 2,169	i would go ahead and replace them. i've never gotten below 16mpg with my car and its heavily modded. you're running super rich from the sounds of it. __________________ '01 GT. P1SC. MMR 900. CMS 2.5 Blower cams. #'s coming soon 2003 Rubicon (DD) 05 Suzuki SV650S 55mpg SOLD Boosted GT Club Founder www.myspace.com/jeepwheelerbob

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November 7th, 2009, 04:27 AM	#4
Huxley Regular 2001 Mustang GT N/A Join Date: Feb 2009 Location: Beaumont, TX Posts: 246	I was having this same problem. I took it to AMMCO for a Fuel Induction. o_o Well...basically they flushed out my fuel system and pretty much cleaned it new.

November 7th, 2009, 06:45 PM	#8
MiddleAgeMustang Newbie 99 GT Convertible 35th LE Join Date: Oct 2009 Location: New England Posts: 30	If I understand them correctly, O2 sensors before the cats are for monitoring A/F ratio. Any O2 Sensors after the cats are just to see if your cats are working. The rear sensors would not be my first place I'd look. This may seem too obvious,but are you hole-shotting everytime you start out? What do your plugs look like? __________________ 35th Limited Edition Mustang GT Convertible, Production #2452 of 4628

November 8th, 2009, 04:10 PM	#9
asiansensation78 Regular 02 GT Vert 15:43.28@25.21 Too many naked bitches in the back Join Date: Jul 2009 Location: Miami Posts: 202	It started getting bad gas mileage after the midpipe was put in. The plugs all look excellent, last time I changed the plugs they had 20,000 miles on them and looked like they were put in last week. I'll check the fuses as ford6693 suggested and go ahead and change the O2 sensors. Should I go ahead and order the extensions too? __________________ Going in as soon as I find a jacked bald guy to sit in my car to tell me I'm granny shiftin' and not double clutchin' like I should Don't want your 75 shot jets anymore? PM me and I'll buy them. Size 40 & 26

November 8th, 2009, 04:27 PM	#10
Pittbull Enthusiast 2001 Mustang GT If you're not first you're last Join Date: Sep 2009 Location: Rock Hill, SC Posts: 588	id def change th eo2 sensors. i had the same problem, im getting 14mpg last time i checked and both my o2 sensors were bad.... i replaced them but have yet to check my mileage __________________ z28 killa Steeda Underdrive Pullies, Accufab 70mm Throttle Body+Plenum, Intake Spacer, Cold Air Intake, Flowmaster Super Flow 44 Series Mufflers, Xenon Quater window scoops, Shorty Antenna, Barely Legal Window tint Work In Progress....

November 8th, 2009, 04:30 PM	#11
Smoothgrandmama Editor/Blue Cyclone 03 Cobra, 09 GT 1 Minute 23 secs @36 mph Join Date: Apr 2007 Location: Willis,Texas Posts: 3,282	Is could be your front o2 sensors...... Thay can affect mileage __________________ 360 MM Gaming Crew

November 8th, 2009, 09:17 PM	#12
asiansensation78 Regular 02 GT Vert 15:43.28@25.21 Too many naked bitches in the back Join Date: Jul 2009 Location: Miami Posts: 202	Ok, fuse is good, so I ordered 2 front O2 sensors, will install as soon as they get in. Do I need extensions as well? __________________ Going in as soon as I find a jacked bald guy to sit in my car to tell me I'm granny shiftin' and not double clutchin' like I should Don't want your 75 shot jets anymore? PM me and I'll buy them. Size 40 & 26

November 9th, 2009, 12:17 AM	#13
Pittbull Enthusiast 2001 Mustang GT If you're not first you're last Join Date: Sep 2009 Location: Rock Hill, SC Posts: 588	Idk about the upstream sensors... They look tricky to get to :/ __________________ z28 killa Steeda Underdrive Pullies, Accufab 70mm Throttle Body+Plenum, Intake Spacer, Cold Air Intake, Flowmaster Super Flow 44 Series Mufflers, Xenon Quater window scoops, Shorty Antenna, Barely Legal Window tint Work In Progress....

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