KevFord1993

How? He wont get better mpg or anything o2 sensors either work or thy dont. No median.

dr_bowtie

That statement is False.... you might want to Google how O2 sensors work....

they are made with materials that have a "Shelf-Life" and they wear out...

they work on Millivoltage. .5v to 0v or some work on 5v to 0v but as the materials wear the voltage changes to the point that as the O2 wears it makes the ECU richen the fuel mixture.... if you look at the Live Data of an O2 you can see the life of it as its reading wont be in the Middle road like it should and more to the end of the scale...

pon55

Unhook the dang thing, if no change then it's bad- change- it's working.
We aren't working on the space shuttle.

Warlockk

From what the op has been posting he already knows this but for anyone else following, you wont notice a distinct change just by unhooking the O2 sensor. The engine will run on present parameters instead if responding to air fuel change. Basically it will run in open loop. The only way to tell is by reading the data stream.

Warlockk

Again I think the op knows this so this is for general information. The O2 sensor switches constantly from rich to lean and orders the injectors duty cycle up and down. The faster the switch the better the resulting efficiency. Over time the sensor slows down due to wearing of reactive materials, damage and sediment. Old sensors don't work as well as new ones.

carpdad

I bought BAFX bluetooth reader. Based on amazon reviews. It included EasyobdII cd so I can use the laptop. My eyes aren't that great, so bigger screen helped.
It showed that connections to ecm was good, and showed coolant temp, intake air temp, o2 sensors, maf values.
It showed bank 1 sensors 1 & 2 and bank 2 sensor 1. I assume bank 1 sensors are the 2 upstream o2 sensors and bank 2 is the downstream. If my memory is correct, there is sensor after the manifold connection, sensor after first catalyst then a sensor after the second catalyst. The values were shown and engine running rich. This is at idle. High values were .7 to .8 volts.
Engine rpm was 717-749 at idle.
What was interesting was that the after driving on highway for about 13 miles and at 55 mph, the coolant temp stayed around 174 F. This is about the same coolant temp as when I was idling. Intake air temp was 46.4 F after being on the highway. It is cloudy cool morning. Not chilly.
I have 2 row radiator, 185 thermostat and autozone fan clutch.
I think I have to check the clutch, and possibly go back to 1 row radiator and 195 thermostat.
The radiator and thermostat were changed after the last inspection. I wanted cooler running engine, but they may be too cool, especially this spring being on the cooler side. I have to check the fan clutch, although I haven't come across any definitive way of doing this.

For my info:
1. To change first 2 o2 sensors, it looks like only way I can get the tools in (no impact wrench and I need some beating room) is remove the wheel and the well cover? I managed the 3rd o2 sensor.

2. I haven't removed the kick panel but I do see a blue box under the steering wheel? Is this the ecm? I'm attaching a photo.

Thank you in advance.

carpdad

Something to add:
Hayden brand website says, "...thermal fan clutch engages at about 170 F radiator air temperature (about 30 deg lower than coolant temp)..."

If this is generally true for all thermal switches (autozone Compressor Works 40 mm - may 2012), does that mean that my clutch wasn't being used today? Coolant temp did not go over 176 F.

I have no idea what to check! Only thing I can think of is that outside air is too cool for the test and 2 row radiator may be too much for this truck (1996 4.9L manual 2wd).

Please advise. Should I go back to 1 row and 195 thermostat? Is the 2 row radiator (with cooler ambient air) keeping the engine from reaching operating temp?

Thank you in advance.

sdmartin65

The 185 thermostat is the problem, a 195 will run about 10 hotter so 184 or so. The radiator size is fine. So a $5 fix and you'll be in business.

With your current setup the truck might rarely go to closed loop operation. Don't over think it, the 185 thermostat is 90% of the problem if not all of the problem.

carpdad

Thank you for the reply. I will change the thermostat back to 195.

I also have to change the radiator because the radiator (less than 2 yrs - vista pro 2 row) is leaking. Not bad, but I saw stream coming out after engine shut off. Steam was from where plastic tank meets the fins and from the upper hose side. It does not keep full tank and there is a wet spot on radiator support. I already bought 2 row replacement, but I can return it. Should I choose 1 row? I thought 2 row is added insurance and keeps the engine cooler, but it may be messing with emissions sensors?
The original was 1 row for this 4.9L manual 2wd.

Also, immediately after engine shut off (drove about 20 miles highway - ect average 173 F and iat average 43F), I checked the fan and it was still spinning pretty good. I did not wait for it to stop but it probably went more than 100 spins. I don't know what to think about this. Since the air around it was never operating temp, the clutch maybe never engaged.

After engine shut off, the ect climbed to about 190F.

One thing definite, I will be changing the thermostat.

Again, thank you.

sdmartin65

Just changed my nine month old radiator under warranty at Oreilly. Not sure who sells decent parts anymore?

Go to Hayden website and read up on fan clutches, that sounds normal to me. When not engaged the fan still spins at 20 to 30% of engine rpm. I also warranty returned the fan clutch and got a standard duty clutch and fan that fits a 1990 mustang, way smoother.