Poor Mileage - replace O2 sensor?

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Clement

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My wife's car has been getting very poor mileage for the last few months. It's a 1994 Merc Sable with the 3.0L v6, ~120K miles.

I've checked all the vacume lines, pcv valve, fuel system cleaner, tire pressure. These have helped a bit, especially new tires that actually hold air.

I was thinking about replacing the oxygen sensors just because it's never been done as far as I know.

I was just looking at Advance Auto and Autozone's website and they are saying $50-80 for the sensors. Is that true?

Does anyone know if this car can use a generic sensor that I can wire in myself?
 
Yes, it can, but most generic sensors are about $60 each.

From http://www.rockauto.com you can get an SMP sensor for $40. There are two listed with photos indicating that the difference is the connector at the end, so if you decide to get that one, compare the connector to what you have.

I've used SMP sensors before, they work fine.
 
So a $16 wire-in-yourself sensor like that which is available for GM vehicles would not work for this ford?
 
You may also want to check the condition of ignition components like plugs, wires, cap/rotor, etc. Those also have big impact on fuel economy.
 
if its a Bosch sensor then a voltmeter set on DC can be used to test it. It should swing rapidly between .2and .9 volts. If it doesnt fluctuate rapidly or hangs around .5 volts, replace it.
 
If there were a problem with the oxygen sensors serious enough to see on a voltmeter, rest assured that the check engine light would be on.

That being said, the oxygen sensors have started to slow down well before the check engine light comes on.
 
For $16, I'm almost certain that's a one-wire, non-heated sensor. Ford stopped using those long before GM did.

You need a heated sensor (which contains a heating element so it starts working sooner after startup) for the Sable and that adds about $20-$30 to the price.

Don't ask me why a heated OE sensor is cheaper than a heated generic sensor; I've been trying to figure that out for a while.
 
Get the correct part for the car. If you cant afford proper maintenance, then dont use a vehicle. Cheaping out on $16 parts more often than not causes more issues down the line... I'd highly suggest you not do it. Wire yourself sensors arent the best choice by a long shot because you have to have an additional connection, which is often succeptible to corrosion, etc.

Ford vehicles used to at least use a lot of bosch parts... you might be able to get a real bosch yellow box part at a better price than the ford part... But use the internet - Im sure there is a ford dealer that does wholesale to the public over the internet - there is same for most other car brands.

A lazy O2 sensor could be your issue, or the engine could just be 'tired' by 120k though, youre likely near due...

JMH
 
JHZR2 - Dude, calm down, don't give me that crap. That's uncalled for. The transmission is a bit touchy too. I can't afford to replace that either, does that mean I shouldn't have a car? Likewise I'm not going to spend $50-$80 each on O2 sensors to save a couple dollars in gas. It ain't gonna happen. However if a $16 O2 sensor would have worked, well, that would be a possibility.
Take a look at the car info, it is already 11 years old, and a ford! It's not going to last much longer. With that, yeah, it could just be tired.

Seotaji - I'll have to take a look at the EGR system - Thanks for the tip, I never thought about checking it.
 
I'm just a shade tree hack. I grafted in a Bosch 3 wire specced for a 93 5L Ford into my 88 528e which takes a 4 wire. The extra wire is just a drain and I hose clamped it to the body of the new sensor.

I got the replacement from A-zone for 40$. Cheapest on line for OEM was over 100$. I found that the generic Bosch costs more than the direct fit. Reason being that the generic comes with a kit of various type harness connectors. None fit my 528e, so I went with the cheaper one.

My 280k O2 sensor was making the engine run lean and contributing to the car failing NOx. They typically fail opposite to this causing the ECU to richen the mixture.

I butt spliced the leads and taped the daylights out of them. A voltage + ohm test showed that it was putting out specced voltage and no resistance through the splices..... Less than optimum , probably, but the fix has survived nearly 30k and several commutes in 6"+ snow. It is high up on the fire wall and is out of the weather. Besides, If it lasts only 150k , that should be fine.

Chances are a direct fit Bosch sensor can be picked up for about the same price from A-zone. I wouldnt be surprised if it was the same sensor I used. A-zone will also loan you the socket that is used to R+R the sensor.
 
The Mercedes crowd also splices a lower cost $40 O2 sensor into the wiring instead of buying the $120 unit specified for the car.

I'm not positive about this, but I imagine the only difference is the pigtail end of the sensor, and the working end of the sensor is the same. Why pay $80 just for the unique pigtail?
 
I've never, ever, seen a Ford come with a Bosch O2 sensor.

They use NTK sensors, and that has been true for all of the 6 Ford vehicles I've dealt with, ranging in year from 1988 to 1997.

The $40 SMP sensor I mentioned is most likely an NTK sensor..I've ordered 4 of them for Ford vehicles, and all have been NTK sensors, just like the OE sensor.

That being said, Bosch sensors will work fine in a Ford.
 
I have a couple of Bosch sensors sitting on my desk at the moment I salvaged from exhaust work I did for Ford Truck on one of their products from 1993.
 
I just looked up the Motorcraft oxygen sensor for a 1993 F150 5.0L V8 and it's definitely a Bosch.

-


The one for the 1993 Mustang 5.0L V8 is definitely an NTK.

-


All of the Ford vehicles I've dealt with have been passenger cars, not light trucks. It's interesting that the Bosch oxygen sensor is only listed for light truck applications.
 
well, all I will say is that in the BMW community, some folks buy 5.0 bosch parts as replacement for their BMW stuff... as getting it from Ford makes it a LOT cheaper...

That 93 picture looks like a denso to me... similar tip to the one we put in our previa.

JMH
 
quote:
Originally posted by Scotto:
fuel filter?
Click to expand...
I see this reply in many fuel mileage threads. Out of curiosity, how will a fuel filter adversely effect fuel economy?

It is an 11 year old car. The 3.0 2V is tough as nails. I can only think of one internal engine problem (broken cam) in all my years at Ford. It should be getting between 25-30 mpg on the highway.

Plugs- nothing beats factory on it. A platinum (PP suffix) plug is standard. Verify timing, I have run across people who didn't know how to properly set timing, or somehow the distributor slipped and retarded timing on more than one 3.0.

Almost anything will code on that car. AXOD trans will code for a non locking converter/slippage. Check plugs for signs of running rich. Determine how long it will take to amortize your fuel savings by dumping in a bunch of money into parts that may or may not fix it.

At least it isn't a 3.8L, consider yourself lucky on that one.
 
By the way, the large body of the Bosch sensor can make installation difficult in some tight-clearance applications that originally had an NTK sensor, like the rear bank O2 sensor on my 1996 Contour. I used an oxygen sensor socket to remove the NTK sensor, but I couldn't tighten the Bosch sensor down with it because the socket was hitting the firewall before it went all the way over the Bosch sensor.
 
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