Changing O2 Sensors

[tkoforpresident]

Re: Changing O2 Sensors

Thanks for the advice. Did you happen to notice if changing them helped your fuel mileage at all?

i never really kept track of my mpg's, i can tell you however that it took away the problem i had of running very lean in my right bank which is why i replaced them in the first place. =)

[tkoforpresident]

Re: Changing O2 Sensors

I use small wire for my "test" jumpers. Basically a 12 gauge wire with alligator clips attached to the ends.

This would determine if your fan motor is no good.

You would need to unplug the harness from the fan motor and then connect the + and - wires to it to see if it turns on. My test jump wire also has a fuse installed in it just in case it gets grounded somewhere. It works really well.

Since the A/C switch will not activate the fan without freon in it your only alternative is to get the car hot, which I don't recommend. I would go with a manual fan switch.

I am not confident about troubleshooting the PCM and why it is not turning the fan on. However, if this test gets the fan to run then you will be all set if you install a manual fan switch.

thats true, a manual fan switch would work as long as the motor itself did correct?

anyhow, i'm gonna let my car get hot and idle up to 220 degrees plus and see what happens.... wish me luck!

[nascar24jd]

Re: Changing O2 Sensors

i never really kept track of my mpg's, i can tell you however that it took away the problem i had of running very lean in my right bank which is why i replaced them in the first place. =)

I have the opposite problem. I am running rich in both banks. Fuel mileage is 16 local and 20 highway. I think it should do a little better then that but I am really not sure.

[tkoforpresident]

Re: Changing O2 Sensors

it's the first place to start to solve that problem.

[nascar24jd]

Re: Changing O2 Sensors

Man, what a PITA.

I consider myself a pretty good mechanic. I have replaced engines, transmissions, rears, large detroit diesel engines, etc...

This little 3.4L kicked my a$$ today. First off, the 3.4L has exhaust heat shields, so you cannot access the O2 sensor with an adjustable wrench, an open end wrench, or a box wrench. You need an O2 Sensor socket.

So, I bought the O2 sensors and headed home. I have been soaking the manifold with PB Blaster and WD-40 for about 3 days now, so it was certainly well oiled. I put the socket on the drivers side sensor and it would not budge. After getting rather frustrated I moved to the passenger side, which you can hardly even see. I put the socket on along with a universal joint and several extensions. One good pull and it broke free. Easy replacement after that.

Now, 50% there. I moved back to the drivers side. I put on the socket, u-joint, several extensions, and pulled the hell out of it. Would you believe that I broke a Craftsman 3/8" universal joint. When it broke I practically ripped my arm out of the socket. So, now very pissed of I headed inside for bigger tools. I set up the O2 socket, 1/2" u-joint, extensions, and a breaker bar. I pulled for all i'm worth, and now the O2 socket started opening up causing the socket to slip. Somehow it jammed and I just kept pulling. Finally it broke free. When I removed the sensor it was permanently attached to the socket. I tried to get it out put it was completely jammed. I ended up tightening it by hand and then borrowing AutoZone's socket for 1 minute to tighten it up.

I cannot believe that such a simple job turned into such a disaster.

The good news is that the car still runs great. The bad news is that it still smells like it is running very rich. I will know better when I check the fuel mileage after my next fill up. Either way, those O2 sensors were the originals, and were very old.

So, if this does not solve the running rich problem, what next???

[nascar24jd]

Re: Changing O2 Sensors

a 1" adjustible wrench from wal-mart works much better than the O2 socket you got

Not on a 3.4 my friend...

[tkoforpresident]

Re: Changing O2 Sensors

hey nascar, glad you finally tackled those 02's.

i took my bros 02's out of his stock manifolds and they didn't give me that much trouble. that seems like a real PITA.

can't wait to hear your mpg's.

if that doesn't solve the problem, idk what to tell you, perhaps an injectors is stuck open?

thats all i can think of.

[nascar24jd]

Re: Changing O2 Sensors

I took it out for a ride this morning and filled the gas tank. In a few days I will be able to calculate the MPGs. I hope it is better.

Yeah, I can't believe how tight or frozen the drivers side was. Al least it is done now, and I snugged them up but did not go crazy, so next time they will come off easily.

[tkoforpresident]

Re: Changing O2 Sensors

I took it out for a ride this morning and filled the gas tank. In a few days I will be able to calculate the MPGs. I hope it is better.

Yeah, I can't believe how tight or frozen the drivers side was. Al least it is done now, and I snugged them up but did not go crazy, so next time they will come off easily.

they should have come with some anti seize **** on the threads already, but i always add more just for the hell of it.

[nascar24jd]

Re: Changing O2 Sensors

Well... This is a good news, bad news story. The good news is that the car runs just as good as it did before I changed the sensors. The bad news is that the new sensors did not help the fuel mileage at all. Still getting 15 local driving (a/c on and lots of traffic), and about 18-19 on the highway.

The car has 147,000 on it. It runs great, no misfires, plugs do not foul, all around this is an excllent running car. I just wonder why the gas mileage is so bad.

Any ideas...

[tkoforpresident]

Re: Changing O2 Sensors

maybe cuz the 3.4 is a pos??

no really, apparently it doesn't get very good mileage compared to the 3rd gen v6's and the 3.8 4th gen.

[nascar24jd]

Re: Changing O2 Sensors

maybe cuz the 3.4 is a pos??

no really, apparently it doesn't get very good mileage compared to the 3rd gen v6's and the 3.8 4th gen.

Yeah, I will call it as good as it gets. I think if I did not use the a/c then it would probably improve some, but that is not an option.