Suggestions changing O2's appreciated

Hi, this is my first post.

I've been reading posts here for a week or so, and I've been enjoying the way everyone helps each other learn about their vehicles, and maintaining or fixing them. Hopefully I can contribute at some point too. Right now I could use your help and suggestions if you wouldn't mind.

I've recently purchased a '98 Windstar GL with 137K miles on it. It has several problems, but for now:

The questions: 1) with my vehicle, how difficult is it getting to the front O2 sensors, removing and installing them; 2) would it be easier, or necessary, to have special tools for tight spaces, like crowfoot wrench attachments etc, or am I ok with my 22mm 7" long flare nut wrench; 3) is 22mm the right size wrench..

Besides all that, anything helpful would be appreciated.

Thanks very much,
Michael

Your estimate of the wrench size sounds about right. What you may want to do is buy the replacement Oxygen sensor before you remove the old ... that way you know for sure. If you are dealing with original manfacturer sensors, get ready for a pleasant surprise ... they are not difficult to turn ... anti-sieze was used originally ... and you should use some on the new ones ... in fact, some replacement sensors come with the anti-sieze in-place.

You may want to make a 'snubby" wrench by grinding a standard combination wench in-half. These can be really handy. And you can get a special wrench, just for sensors, on the AutoZone tool loan program.

The real question is "Why are you replacing the sensors?".

If you replace your oxygen sensors, I would recommend that you get Motorcraft brand.
You can find them at a good price at www.rockauto.com
You have 4 oxygen sensors, one before each of your 2 catalytic converters (upstream sensors), and 1 after each of your catalytic converters (downstream sensors).
The ones before the converter are used by the computer to keep the correct air / fuel ratio, and are the ones that have an impact on engine performance and fuel economy.
The ones after the converter are used to monitor the catalytic converters to make sure that they are working. That is the only function that they perform.

If you have a problem with a oxygen sensor, your CEL with come on, and you will have a code telling you which of the 4 sensors, and specifically what the problem is.
They do not fail very often.
As an oxygen sensor ages, it will switch slower. They switch from lean to rich (slightly in each case) and the switching rate slows down as they get older. The PCM monitors the switching rate, and if the switching speed gets too slow, you will get a CEL telling you which sensor, and that it is switching too slow.
However, due to the slowing down, I would replace them as a pair.
This way, they will have the same switching charactoristics.

For removal and installation, I bought a "Oxygen sensor socket", which is a deep socket, with a slot up the side. The slot is to make it possible for you to put the socket on over the sensor, and not damage the wires.

Also, when you work under there, make sure that the wiring for the sensors is held up away from the exhaust system.

On my '96, the downstream sensor for the rear most catalytic converter mounted into the back part of the converter case.
When I was changing my "Y" pipe (the dual converter assembly) I removed my oxygen sensors from the old unit and moved them to the new unit.
When I applied a gentle turning only pressure to that rear sensor, the whole mounting nut broke right out of the converter body.
This would have been a major mess for me, had I not been changing the converter assembly anyhow.

One important note, if you get a P0171 and / or P0174, the most common cause is a vaccum leak into the intake of the engine. Another cause can be one or more dirty injector(s).
These codes are rarely caused by an oxygen sensor, although parts people often try to sell you oxygen sensors for that.

Although I wouldn't normally DARE disagree with wiswind, I would add that Ford does not manufacture their O² sensors. They are sourced externally. If you open the Motorcraft box and see the familiar Bosch part number sequence on the "Motorcraft" sensor (in addition to the Ford part number), don't be too shocked.

That said, be very careful about your replacements. Using an aftermarket (Bosch) sensor has never been a problem for me, but IF you decide to do this, avoid the "universal" sensors and get the Bosch sensor designed as an "exact fit" OEM replacement. It is more likely to have the correct fluting on the sensor tip, correct tip reach into the gas stream, and proper lead length and connector. The connector is less of an issue for sensor performance and more of a convenience, but the tip length and fluting on the protective cap can be critical.

You might also want to get a supply of antiseize compound to apply to the sensor threads when you install, since the little dab of compound that is usually applied to the sensors as purchased is seldom enough. Just make sure you keep the compound off the sensor tip.

Thanks very much for the replies and advice, this is a great place and I think I'm hooked already.

Regarding why I'm changing the sensors: I just got this '98 Windstar with 137K on it, and I have no service records for it, although I think it's been pretty well maintained. I got a P0153 code, I reset, and I'm waiting to see what comes up again- there have been several MIL's, and I just recently picked up an OBDII reader. So, we'll see.

Rather than dealing with a hot exhaust, and checking for voltages etc, at this vehicle mileage I thought replacement O2's might be easier and a good thing to do anyway.

I already bought a pair of upstream sensors, not Motorcraft or Bosch, and maybe it was a mistake, I'll post.

I haven't crawled under there yet, wiswind you mentioned that there was room for a deep socket O2 wrench under there, upstream included, am I correct?

Thanks everybody.

Hello

At times I've had trouble getting a bad O2 sensor out. It's going to be thrown away anyway, so I cut the wire off and was able to use a regular deep socket or a box end wrench to get a better grip. My sensor socket couldn't handle the torque the required to get the senor out.

Food for thought.

Dan

Thanks Dan,

I appreciate that idea, and it might get to that. Today, after clearing it last week, I got the P0153 code again, so I'll definitely be crawling underneath to see what's what this week.

P0153 is Heated Upstream Oxygen Sensor slow response on bank #2.
Bank #2 is the front bank of cylinders.
Easy way to remember which bank is which is to remember Bank #1 is the bank that has Cylinder #1.

Blue Bowtie, you are more than welcome to correct me anytime....
1. I make mistakes and 2. I am not a mechanic.....and am trying to learn as I go.

It is correct that the oxygen sensors are made by Bosch, but as Blue Bowtie points out, you want to make sure to get the correct OEM specified sensor.

I would go ahead and replace the pair of sensors (bank 1 and 2 upstream sensors).
I soaked the threads of my sensors with P Blaster penetrating oil several hours ahead of working on them.
I was able to get the deep socket (oxygen sensor socket) onto the sensors.

I would also wonder why the sensor failed.
Yes, it is old, however the sensors on the windstar are pretty reliable.

Point being, you don't want to have the new sensors fail due to a problem that could be present.

When you remove the sensors, look very carefully at them.
If there is a green stain on them (assuming that you are using the traditional green coolant), then you have a coolant leak into the cylinder(s) on that bank.
Coolant will cause your oxygen sensors to fail.
The most likely cause of coolant leakage into the cylinder(s) on a 1996 and newer windstar is the lower intake manifold gaskets.
You will want to replace them if they are leaking.
Get the replacement gaskets from FORD, as they have made improvements to them (more reliable) that are not yet available in the aftermarket.
The head gaskets are much more reliable on the post 1995 windstar, and are most likely still good.

The other thing to be careful of is that any RTV sealant that contains silicone on the engine, as that can also cause oxygen sensors to fail.
RTV sealant for use on the engine must be silicone free, and clearly labeled as "sensor safe".

Thanks wiswind,

The P0153 code came back yesterday, so it wasn't a fluke. I'll follow your advice when I get to it, which may be next week since I'm wiped out from replacing the power steering pump these last few days.

I had a VERY bad time getting to the bracket bolt which is beneath the pulley, Haynes was absolutely no help as you probably know. Today I saw some of your Windstar pictures including the P/S pump one, and if I had seen it before I attempted the job I could have asked your advice and probably saved a lot of time and effort. Such is life.

Once I get to the O2's I'll post again. Thanks.

Another note, you do not want to get oil, undercoating, etc onto the outside of the oxygen sensor case....like where the wires go in or any holes on a sensor that you are keeping.
This is because the sensor works by a chemical reaction caused by a difference between the oxygen level in the exhaust and in the air outside.
So you don't want to seal out the outside air from the internals of the sensor.

Instead of cutting the wire, you can simply unplug it, slip the connector through the box wrench, and have your way with it. Some of the older Ford connectors were ridiculously large, and wouldn't fit, but it seems that since about the mid-'90s they switched to mostly WeatherPacks and elimimated that issue.

Thanks again guys,

I'm doing a few more diagnostics before replacing the O2's, thought that might be wise.

I appreciate the help and will post when I get to the next step.

Can you tell me if I've correctly identified the P0153 upstream bank 2 oxygen sensor?

According to what I've read in posts here, that should be the sensor that's easily visible when looking down behind the radiator, while standing in front of the vehicle, yes?

Can you tell me if I've correctly identified the P0153 upstream bank 2 oxygen sensor?

According to what I've read in posts here, that should be the sensor that's easily visible when looking down behind the radiator, while standing in front of the vehicle, yes?

Yes you are correct . Bank 1 is cylinders 1,2,3 along firewall, bank 2 is cylinders 4,5,6 in front (1 and 4 are the "passenger" side ends, or what Ford calls the front of the engine)

Thanks busboy4,

That was important to know, I sure don't want to fight with these sensors, then find out I tested or removed the wrong ones.

I appreciate it.

Well, I did my homework today regarding code P0153, here on AF, and also on the internet. It may have fried my brain a bit (stoichiometric air-fuel ratio anyone?).

It appears, and this is wishful thinking of course, that something as simple as lousy fuel may have been activating this code. My Windstar sat for 'a while' before I bought it in April, and it had maybe 1/4 tank of fuel in it at that time. Also, I've been reading that present day ethanol and methanol additives attract water to the fuel tank. Anyone know about this? And is there a tried and true water eliminating additive anyone could recommend?

The plan, which has been changing quite a bit, is to test the offending sensor if the code comes up again (eight days now, no problems). I'll need to figure out how exactly to 'backprobe' the sensor. Haynes just says 'do it', but hopefully someone here has left some guidelines. I understand that you can fry a sensor by testing it the wrong way.

Thanks for all your help everyone, it's very much appreciated.

Regards,
Michael

I would run a tank or so of fuel with some Chevron Techron cleaner in the tank.
If the code does not come back, don't worry about it....may have been caused by the vehicle sitting, as you said.

Thanks wiswind, will do..

An update:

I followed wiswind's suggetion and put in Techron plus tried to run off the top half of the tank for around 250 miles, so far no more codes at all over more than three weeks, including the P0151 that I had previously every week or so.

I had bought a recently infrequently used Windstar, which may have caused the problem, plus junk in the fuel tank that gets used when fuel is low.

Whether or not this is fixed, and I'll post again if not,asking for help no doubt, I'd like to thank everyone who's helped me with this one. I've got a feeling this may have been a simple fix. We'll see.

Best regards to all who helped.

In previous message, I meant code P0153. Thanks all.