O2 sensors and 3.8 L engines - TCCoA Forums
 
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post #1 of 22 (permalink) Old 10-31-2005, 05:15 PM Thread Starter
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O2 sensors and 3.8 L engines

Hey Folks:

Any one know how many O2 sensors a 1993 T-Bird has? It is reasonable for me to assume that an 1993 Sable or Taurus would have the identical number (my winter car)?

94 T-Bird LX
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93 Mercury Sable
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post #2 of 22 (permalink) Old 10-31-2005, 05:28 PM
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two, one before each cat. the fwd 3.8s im not sure of. i want to say they have one before the cat, maybe another after it.

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post #3 of 22 (permalink) Old 10-31-2005, 07:02 PM
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well they HAVE to have at least 1, my vote would be 1, but thats a guess.
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post #4 of 22 (permalink) Old 11-01-2005, 09:40 AM Thread Starter
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Ok, that's one more than I thought.....

For my next question, my car is getting poor milage. Wires, cap rotor, plugs are all less that one year old and have less than 10,000 mi on them. (All Motorcraft). I'm told that 02 sensors are a maintanance item and should be changed every now and them. So.... which sensor to change? Or change both of them?

94 T-Bird LX
3.8 V6 - Bone Stock! (Bye darlin' I'll miss ya!)
93 Mercury Sable
03 Mercury Marauder
88 F-150 XLT Lariat
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post #5 of 22 (permalink) Old 11-01-2005, 10:01 AM
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unless the o2's are throwing a code I wouldnt worry about it yet. they are a bit spendy to just replace, but I would probably change the fuel filter first, and run some injector cleaner through it. Seafoam or Lucas.
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post #6 of 22 (permalink) Old 11-07-2005, 06:02 PM Thread Starter
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SIGH......

Took it in to Ford for a recent check engine light... turns out my ECM is toast as it will not respond to the scanner. Tried it with my buddy's Snap-On scanner and it won't talk either. I'm trying to get a replacement ECM one from the junkyard, but everyone seems to want the Ford part number (which Ford tells me is essentially useless and as these computers must be ordered by the calibration code). So, I've decided to pull the ECM, get the Ford PN to pacify the wrecker, then make the wrecker open the computer and I'll compare calibration codes by looking inside the computer (or so my dealer's parts department tells me so)

One issue though... and I could use some help here. The computer seems to be pretty easy to pull, but I can't figure out what's holding the darn thing in. There's one very obvious bracket (which I've pulled) and I though the ECM would just pull out. Apparently not so and I don't want to go in to gorilla mode just yet.

Anyone pulled an ECM on a 1992-1995 Ford Taurus or Mercury Sable? There's obviously something simple I can't see, cause the manual says 0.4h R&R time.

Thanks all who've responded so far for your help. I'll try and quit posting Mercury Sable questions here, and get back to my T-Bird next post

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post #7 of 22 (permalink) Old 11-10-2005, 12:01 PM
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Two O2 sensors for the pre-96 cars, as I recall.

Did you disconnect the harness from the EEC yet? It's a pretty massive harness, and that could hang the unit up.

Isn't there a sticker on the EEC with the part number and calibration code? I wouldn't expect to have to open it up.

Maybe you should try cleaning your MAF sensor and testing your ECT sensor (a voltmeter or ohm-meter is sufficient). Those could impact mileage significantly.

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post #8 of 22 (permalink) Old 07-05-2006, 03:39 PM
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Ok thread resurrection time. Helping my sister out with her 97 3.8 t-bird (my old one). I've worked with the 4.6 for so long now that the 3.8 is a mystery to me. How many 02 sensors does this engine have and where? The 4.6 has four, one per side before each cat, and one per side after each cat. I assumed the 3.8 was the same way, but could be wrong. Anyone want to help me out here?


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post #9 of 22 (permalink) Old 07-05-2006, 07:19 PM
 
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I took this straight out of the tech articles on this website......

Oxygen Sensors
The oxygen (o2) sensors upstream won't affect fuel mixture unless they are contaminated or damaged, causing them to switch slow or stay rich or lean all the time. They measure oxygen in the exhaust and create a electrical signal from 0.0 Volts to 1.1 Volts; 0-.5 Volts LEAN, .5-1.0 Volts RICH.

The PCM adjuts fuel trim from this data. The rear catalycs senors (OBD II) will work the same but are only used for federaly mandated catalyst efficiency monitor test. This test tells the PCM if the CATS are present and working properly and will turn the Check Engine light on if all is not well, after seeing this fault during one or more drive cycles. BLAME THE FEDS FOR This ONE!!!

All the 3.8L engines have 1 oxygen and 1 OBDII sensor.
All the 4.6L engines have 2 oxygen and 2 OBDII sensor.

The functions of each of the 4 wires going to the O2 sensor:

1. 12v + heater element
2. heater element ground
3. 5v + EEC reference signal
4. sensor signal return (to EEC)

You can distinguish between the heater element ground and the signal return by wire color or by disconnecting the EEC. The heater ground will still have contunity while the signal return will be open.
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post #10 of 22 (permalink) Old 07-05-2006, 07:32 PM
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Ok, thats what I would have guessed, and thats what the book at AutoZone said to (one of each). But when my sisters boyfriend looked to replace the O2 sensor, he found two of each type under there. One for each side like a 4.6 has. Anyone have an explanation fo that?


1997 Thunderbird Sport
Low Miles
Wifes Car
destined to remain stock

1997 T-Bird GT 4.6
80 MM Mustang GT MAF - P&P'd Mustang GT TB and Intake Plenum - PI Intake manifold - PI Heads
Mark VIII Torque Converter - J-Modded 4R70W transmission - Mark VIII Aluminum Driveshaft - 3.73 gears
PBR Brake Calipers - Eibach Springs - KYB Shocks
'89 SuperCoupe front and rear sway bars
SCT Chip programmed by Lonnie Doll
255/50/16 Falken Ziex ZE-512's
True Dual exhaust with Magnaflow DI/DO muffler
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post #11 of 22 (permalink) Old 07-05-2006, 11:31 PM
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thats a little wrong though. All OBDI 3.8L's have 2 oxygen sensors. All OBDII 3.8L's have 2 oxygen sensors and 1 OBDII sensors.

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post #12 of 22 (permalink) Old 07-05-2006, 11:34 PM
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Ohh ok. So a 97 model (Which would have OBD II) would have two O2 Sensors. I'll forward the info to my sis. Gracias!


1997 Thunderbird Sport
Low Miles
Wifes Car
destined to remain stock

1997 T-Bird GT 4.6
80 MM Mustang GT MAF - P&P'd Mustang GT TB and Intake Plenum - PI Intake manifold - PI Heads
Mark VIII Torque Converter - J-Modded 4R70W transmission - Mark VIII Aluminum Driveshaft - 3.73 gears
PBR Brake Calipers - Eibach Springs - KYB Shocks
'89 SuperCoupe front and rear sway bars
SCT Chip programmed by Lonnie Doll
255/50/16 Falken Ziex ZE-512's
True Dual exhaust with Magnaflow DI/DO muffler
<<< SOLD >>>
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post #13 of 22 (permalink) Old 07-06-2006, 12:14 AM
 
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my 97 has 4 of em... 2 in the cats and 2 in the pipe before the 3rd. the latter two i never knew existed until just a few days ago.
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post #14 of 22 (permalink) Old 07-06-2006, 12:27 PM
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89-95 have 2
96-97 have 4 (2 before and 2 after the cats)

You engine won't throw a check engine light until the O2's are WAY too slow. If you have 100k on them, REPLACE THEM. Point in case, my 97' Mark VIII with 131k on the odometer. One O2 was cracked and I replaced it, the New one switched twice as fast as the other one that still has 131k on it so I replaced that one also. My around town mileage went from 19mpg to 22mpg which is a pretty good increase.
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post #15 of 22 (permalink) Old 07-06-2006, 04:45 PM
 
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Quote:
Originally Posted by Thomas
thats a little wrong though. All OBDI 3.8L's have 2 oxygen sensors. All OBDII 3.8L's have 2 oxygen sensors and 1 OBDII sensors.

Could you update that article then?
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post #16 of 22 (permalink) Old 07-06-2006, 06:34 PM
 
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I'm with rancherlee here.I have a 96 Cougar, w/ 2 - O2 sensors before the cats, and 2 OBDII sensors, 1 after each cat just before the Y. I priced them at about $45 for the O2's and $60 for the others or vice versa, but that' each sensor. Reinforcing the fact that just replacing them w/o proving them at fault could cost a bit,just over $200.
If you pull the codes, I believe it will at least tell you which bank the code is coming from. It's possible it blew a head gasket once, and only one side has bad sensors.
Good luck!
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post #17 of 22 (permalink) Old 07-06-2006, 07:02 PM
 
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hold up here, the two sensors past the cats before the 3rd cat arent the normal run of the mill 60$ O2 sensors?
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post #18 of 22 (permalink) Old 07-06-2006, 07:41 PM
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I think they are, but they don't trim the fuel mixture, they just report that your catalytic converters are shot / removed (the ECM measures the difference 'twixt the fronts and the rears and decides if there's a functioning cat in between).

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post #19 of 22 (permalink) Old 07-06-2006, 09:20 PM
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Quote:
Originally Posted by wmullen1
.....If you pull the codes, I believe it will at least tell you which bank the code is coming from. It's possible it blew a head gasket once, and only one side has bad sensors.
Good luck!
My sister had the codes read at an autozone. They read the codes right, but she didn't mention it saying which side was bad. But then these are the same geniouses to told her there was only two sensors on the car. I told her to go back, take the WRONG part they sold her, and tell them it is an OBDII car and has a total of FOUR sensors and to get the two front sensors for the car. The rear don't really effect how the car is running.


1997 Thunderbird Sport
Low Miles
Wifes Car
destined to remain stock

1997 T-Bird GT 4.6
80 MM Mustang GT MAF - P&P'd Mustang GT TB and Intake Plenum - PI Intake manifold - PI Heads
Mark VIII Torque Converter - J-Modded 4R70W transmission - Mark VIII Aluminum Driveshaft - 3.73 gears
PBR Brake Calipers - Eibach Springs - KYB Shocks
'89 SuperCoupe front and rear sway bars
SCT Chip programmed by Lonnie Doll
255/50/16 Falken Ziex ZE-512's
True Dual exhaust with Magnaflow DI/DO muffler
<<< SOLD >>>
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post #20 of 22 (permalink) Old 07-15-2006, 02:15 AM
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ok, so let's see, according to what I've read, 89-95 have 2 oxygen sensors. 96-97 have 4, 2 before the cats and 2 after. Ok, cool! I'm pretty much in the process of changing my O2 sensors, so question, are they easy to change, or, should it be done by professional, also, any preparations that should be done before chaging them? Thanks!
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post #21 of 22 (permalink) Old 07-15-2006, 12:34 PM
 
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most popular autopart stores will rent you the socket that makes changing them a breeze. And, as long as you can get up under the car easily with some room to spare, its pretty simple. Probably a 30 min. job. as long as they are cool, longer if their hot.
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post #22 of 22 (permalink) Old 07-16-2006, 12:44 AM
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oh, ok, cool. Thanks! with the T bird, I'm sure I could get under it. Thanks!
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