O2 Sensor Help

mustangfu · April 4th, 2008, 11:12 PM

So I've got a 94 GT with 125,xxx miles. Fuel mileage is low, power output is bogging, and when i start it cold, the idle is rough.

Easy symptoms of a bad o2 sensor, so I've been told. So, I went to O'Reilly's and bought a new one.

Then I realized, I don't know a damn thing about sensors, I've been driving 40 year old cars my whole life XD

Where is it and how do I replace it? lol

Thanks,
Will Z

Assassin_Dan · April 5th, 2008, 06:24 AM

Well to start there are 4 of them and they are screwed into your exhaust system, 2 of them before the cats, right near the base of the header I beleive, and 2 of them after the cats. To change them you must be able to get under the car to disconnect the wires and unscrew them. Then screw in the new ones and reconnect the wires.

97Cobra · April 5th, 2008, 06:39 AM

make sure you get a special 02 sensor socket. its a normal socket with a side missing so the wires can hang to the side while you take the old ones off n put the new ones on. saves a lot of time n effort if you buy the socket. the 2 02 sensors after he cats are easy the ones on the exhaust manifolds are somtimes a pain. make sure to spray them with PB break loose 20 min before you try them. it helps! best to replace all 4 because when one goes the rest are sure to follow with stock 02s.
also you might want to clean the MAF, get a new air filter, replace the fuel filter (easier than it sounds), and buy new spark plugs and possibly wires too. and that should help you out A LOT!

mustangfu · April 6th, 2008, 01:15 AM

i wish i could afford 4 lol, the one was like 77 bucks. and ideas on how to tell which one is bad?

97Cobra · April 6th, 2008, 02:51 AM

it would have to throw the check engine light and you would have to hook a OBD II code reader and pull the codes to tell which one... could you buy 1 more. I would replace the ones up by the manifolds first because they seem to go bad before the others...

mustangfu · April 9th, 2008, 10:49 AM

yeah i can do that. oh, and i hooked up a code reader to it, and couldn't get any readings! i know i was doing it right...it's obdII right?

Assassin_Dan · April 9th, 2008, 09:27 PM

A 1994? Not 100% sure but I think they were OBDI, 1995 or 1996 was the first year for OBDII.

April 5th, 2008, 06:39 AM	#3
97Cobra I Post Entirely Way Too Much 1997 Mustang Cobra 1/8 - 8.89@86mph Join Date: Jan 2006 Location: Wyoming Posts: 6,515	make sure you get a special 02 sensor socket. its a normal socket with a side missing so the wires can hang to the side while you take the old ones off n put the new ones on. saves a lot of time n effort if you buy the socket. the 2 02 sensors after he cats are easy the ones on the exhaust manifolds are somtimes a pain. make sure to spray them with PB break loose 20 min before you try them. it helps! best to replace all 4 because when one goes the rest are sure to follow with stock 02s. also you might want to clean the MAF, get a new air filter, replace the fuel filter (easier than it sounds), and buy new spark plugs and possibly wires too. and that should help you out A LOT! __________________ Modifications and pics in my Garage... Reps Appreciated!

April 6th, 2008, 02:51 AM	#5
97Cobra I Post Entirely Way Too Much 1997 Mustang Cobra 1/8 - 8.89@86mph Join Date: Jan 2006 Location: Wyoming Posts: 6,515	it would have to throw the check engine light and you would have to hook a OBD II code reader and pull the codes to tell which one... could you buy 1 more. I would replace the ones up by the manifolds first because they seem to go bad before the others... __________________ Modifications and pics in my Garage... Reps Appreciated!

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April 5th, 2008, 06:24 AM	#2
Assassin_Dan Regular 1998 Mustang V6 Join Date: Oct 2007 Location: British Columbia, Canada Posts: 126	Well to start there are 4 of them and they are screwed into your exhaust system, 2 of them before the cats, right near the base of the header I beleive, and 2 of them after the cats. To change them you must be able to get under the car to disconnect the wires and unscrew them. Then screw in the new ones and reconnect the wires.

April 9th, 2008, 09:27 PM	#7
Assassin_Dan Regular 1998 Mustang V6 Join Date: Oct 2007 Location: British Columbia, Canada Posts: 126	A 1994? Not 100% sure but I think they were OBDI, 1995 or 1996 was the first year for OBDII.

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