Problems with the o2 sensor

[bmacd]

My explorer has been killing me financially in gas bills in the last couple of months. I've posted before about my o2 problems, but got no results.

The error code told me which sensors to replace (2 out of the 4), and I did that. Unfortunately, after I manually cleared the code out, it returned. I'm getting close to 8mpg, and i'm getting to the point of taking it into the stealership to fix this.

It's a '96 v8, and the problem was occuring on the left side of the car, and i replaced both sensors (before and after the cat). The wiring appeared to be in tact, but is there something that i could be overlooking?

HELP!!!!

-=bmacd=-

 

[Alec]

O2 sensor codes do not mean to just replace the sensor. They can often be thrown due to other problems.

Is your exhaust itself intact? Any leaks? Exhaust manifold gaskets?
It could also be due to other sensors.

I'm guessing though that your exhaust manifold is cracked or the gasket needs to be replaced.

 

[bmacd]

i know the exhaust gasket is bad, but i was under the impression that it would not affect anything else in the car. There is a loud ticking noise (the opening and closing of the exhaust valves) and a mechanicly inclined buddy said he had the same problem on his mustang, but it was "just a noise" and would never escalate to any other problem.

When i had the trouble code read at Autozone, it was for the o2 sensors that i had already replaced. The same code registered before and after replacing the sensors.

-=bmacd=-

 

[Alec]

The exhaust leak could be so bad the O2 sensor readings to the computer aren't what the computer is expecting, thus it throws the code.

Since it's only 1 bank this leads me to believe it's not a problem somewhere else in the truck (MAS, etc).

 

[V8BoatBuilder]

Alec is dead on.

It would help if you could post the codes you're getting. If the gasket leak was real bad, the sensor may say the engine is running lean, and richen up the mixture, casuing bad mpg (and killing your cats).

 

[bmacd]

it's been awhile since i've had the code pulled, and i'm looking over my receipt that Autozone prints for you, but not having any luck finding the specific code #. The receipts just show "before the cat, driver's side" and "after the cat, driver's side", BUT, the younger guy who scanned my car forgot which side it was on, so he also printed it for the passenger side too (same o2 sensors, just passenger side instead of drivers).

I know this doesn't help you guys a whole lot, but when Alec initially mentioned the exhaust gasket, everything seemed to make perfect sense.

-=bmacd=-

 

[V8BoatBuilder]

FPN has gaskets for 6 bucks.... I just ordered and installed some.

I haven't had any problems with them, but many members have. They all seem to upgrade to Percy's Dead Soft Aluminum gaskets. You can get them at Summit Racing.

 

[97BlackX5.0]

you think maybe you replaced the wrong O2 sensors cause the kid printed out the wrong side...i ran around with an O2 sensor problem for about 10k miles.... it didnt affect mileage very much at all..... in fact it seemed to be better sometimes... i had the first sensor on the drivers side and the second sensor on the passenger side out.... other than that it sounds like a bad fuel pressure regulator.... or like they were saying the bad exhaust leak....

 

[bmacd]

i replaced the correct side of the o2 sensors. What other problems are associated with the exhaust leak...like bad or rusted flanges? I don't want to start this project hoping to only replace the gasket only to find out I need to weld new flanges on...

-=bmacd=-

 

[V8BoatBuilder]

Bmacd sent me a PM, asking about replacing the gaskets. Rather than just reply to him, since I installed gaskets a few weeks ago, here is a breif writeup about just replacing the gaskets:

In june I had to replace my head gaskets and do a valve job, to get the heads out you need to remove the headers.

Look at my thread "Help Diagnose my Intermittant Missing Problem" in the Under the Hood section for some photos of the heads removed, etc.

You should be able to replace the gaskets with basic tools and a few hours time. Here's what I would do:

1) Remove the fenderwall plastic linings. There are screws and bolts.

2) Lubricate the manifold to head bolts (2 per cylinder) with PB blaster, and use a metric (forget the size, I think stock is 14mm) socket to get the bolts out. You'll need extensions and u-joints, and a breaker bar. An air impact gun will help the process, but is not needed. On the driver's side, it helps to remove the 13mm bolt in the steering shaft and collapse the shaft out of the way.

3) With the bolts out, you should be able to move the manifold away from the heads a tiny bit, enough to get the old gasket out and the new one in. However, if the old gasket does not come out cleanly, and I suspect it won't, you need to remove the manifolds all together.

4) On a 96 with internal egr, all you have to do is unbolt the collector bolts. There are two per header. Again, you'll need extensions and u-joints.

5) You'll want to use a torque wrench for putting it all back together.

That's it!