oxygen sensor

[wll123345]

Alright i hope someone here can give me some information about my car. If i take my explorer on a trip 30 minutes or longer traveling at highway speeds my cel comes on. It gives the code 176 and 177 when i check it. This is the only time it comes on. I'm not sure if the sensor needs to be replaced or if another condition exists that is causing these readings by the 02 sensor. If anyone can offer any insight it would be greatly appreciated. O yeah, and the explorer has 70780 miles on it. thanks.

 

[MrShorty]

If it helps you feel better, I don't know if the sensor needs to be replaced or if another condition exists that is causing out of range O2 sensor data. A trouble code by itself is rarely enough information to go on for that kind of determination.
Because you only give the two code numbers, I'm going to assume that they are continuous memory codes, that the EEC-IV system passed the KOEO portion of the test, and that you haven't run the KOER test yet. If my assumptions are correct, the next thing I would do is perform the KOER test to see how intermittent the fault is.
There's an interesting contradiction between those two codes. 176 indicates a lean reading (O2 signal <0.4 V) and the 177 indicates rich (>0.4 V). If it passes the KOER test, I would clear the continuous memory codes (disconnect jumper anytime during KOEO or continuos memory code output), drive the truck until the CEL comes on, then check the codes to see if a) the 176 comes back, b) the 177 comes back, c) both come back, or d) something else comes back. I might even do it three or four times to see if it gives me a consistent answer.
In addition, you could put a fuel pressure gauge on the fuel rail to make sure the fuel pressure is where it should be. Also make sure the fuel pressure regulator isn't leaking into its vacuum line.

 

[wll123345]

thank you very much for your help. I did only preform the koeo test to give me the codes stored in memory. I figured the koer test wouldn't help me much because the check engine light only comes on when driving. I also did reset the memory and the same codes came back. I have two 02 sensors and only the left side (bank 1) is picking up a fault in reading, thats why i am wondering if maybe its just a bad 02 sensor. If something like the fuel pressure was wrong or there was a vaccum leak i would think both sensors would be picking up a rich or lean reading.

 

[Glacier991]

FWIW... your helper here... Mr. Shorty.. is among the best and the brightest you could find..... listen up!!!! He really knows his stuff!

 

[wll123345]

yes he does sounds like he knows what he is talking about. I am going to check the fuel pressure tommorow and check for a leaking regulator. I was just wondering why only one sensor is picking up an error and the other isn't. it just seems like it is something else besides the regulator. The regulator supplies the same amount of fuel to both sides of the engine, so if the regulator is faulty both 02 sensors should be sending errors. (right?) any thoughts on this?

 

[MrShorty]

You're assumption that an error in fuel delivery would show up in both sensors rather than one is a probably a pretty good assumption. Personally, as easy as it is to check the fuel pressure and verify that fuel delivery is what it should be, I prefer not to go on the assumption that it's good, but rather to verify that it is good. Sometimes knowing what is working can be just as valuable as knowing what isn't working in diagnosis.
The assumption that a vacuum leak would affect both sides of the engine equally is perhaps less valid. The 1st gen 4.0 OHV is known to develop vacuum (and other fluid) leaks through the lower intake manifold, and it seems to favor the driver's side, in particular the #5 cylinder. Still, it might not be the real problem, but verifying that there are no vacuum leaks can be a quick way to eliminate one possible cause.
I just had an interesting idea. What would happen if you switched the O2 sensors? Would the trouble code follow the O2 sensor or not? In suggesting this, I'm assuming the 2 O2 sensors are the same.

 

[wll123345]

I think i found the problem with the 02 sensors. I went to inspect my 02 sensor when i noticed that the wire leading to the connectino had a chunk taken out of it. I need to buy a new 02 sensor now since there is no way of just replacing the wire. This brings me to a new problem though. Should i buy a bosch one or should i get the motorcraft one from the stealership? I was researching this on the board and heard some bad things about the bosch 02 sensors. any suggestions on what kind i should get?