O2 Sensor failing on trip home

[Forder]

Hey guys, I don't expect much help with such short notice and the short time frame I have until I leave again in the morning, but I would greatly appreciate it!

So I'm on my 850 mile trip back home to NY from KY for the holidays and about 1/3 way into it, my truck starts throwing the CEL intermittedly. Seeming to turn on when on flat/downhill roads. Going uphill it would go off, but I had reduced power. When I stopped for gas (which was sooner than normal), it was idling rough at around 600 RPM. We stopped half way through the trip (where I am now) at a hotel and I tried the paperclip trick to give me the CEL code(s). It gave me a 176 and 177 code which is "Oxygen sensor not switching - system is or was lean Left or Front HO2S - Fuel control" and "Oxygen sensor not switching - system was rich Left or Front HO2S - Fuel control" respectively.

So now that I know what it is exactly, what do I need to do to fix it? It's been well below freezing the whole trip so I dunno if that's affecting it. But I drove to KY in an even worse snow storm and lower temps with no prob. Is that the sensor on the intake manifold? Would replacing it help? I'd really like to fix this in the morn if possible for the rest of my trip (400+ miles).

Thanks A LOT in advance for any help provided!

 

[Tbars4]

...This might help...
http://www.explorerforum.com/forums/showthread.php?t=65524&highlight=176

...Or this...
http://www.explorerforum.com/forums/showthread.php?t=249502&highlight=176

 

[Forder]

...This might help...
http://www.explorerforum.com/forums/showthread.php?t=65524&highlight=176

...Or this...
http://www.explorerforum.com/forums/showthread.php?t=249502&highlight=176

Sweet, thanks Tbars, you always help me out .

That enlightened me a little. I'm pretty sure I don't have an exhaust leak anywhere, but I'll check in the morn. Where are the left/right 02 sensors at? It's not the MAF sensor on the intake manifold, is it? Maybe I can get away with re-seating them like the guy in that second link. I also don't think it's a vacuum leak because it runs good cold and starts acting up after it gets warm like after I gassed up and ate it was good for a little bit, but then started throwing the CEL and running rougher after some highway cruising.

Thanks again!

 

[Forder]

Bout to leave in 30 mins, any more help would be extremely nice!

Thanks!

 

[MrShorty]

Where the codes only point to one side, I wouldn't expect it to be a problem with the MAF, because that would affect both sides.

One thing I like to recommend when you are getting a code for one side is to swap the two O2 sensors then test drive it. If the code follows the sensor (in your case if it shows up on the right side after switching), then you can be pretty sure the problem is in the sensor itself. If the code doesn't follow the sensor, then you can start looking at other things.

 

[92exp4x4]

I have a similar issue with my Mustang. I have not replaced it yet but I'm going to put an O2 in it when its warms up a bit. I tuned it up and it has seemed to help so far. I have been fighting this for a while now.

 

[Forder]

Well after I gassed up and left the hotel to continue the trip, the truck has fixed itself somehow. I've drove 150 so far (topping it off and refreshing) and I haven't got any CEL, power is restored and I'm getting decent milage. So I dunno wtf it was. Mabye I had bad gas and the extreme cold was messing with it? Even though I'm driving in t degree snowstorms still. Gotta go now though, thanks so far, guys.

 

[Forder]

Well 2 years later and this issue comes back. It seems to only have a problem in the winter time when it's really cold out (below freezing). The other day when it was 10 or so degrees out, it wouldn't even start after cranking it for 5 or so mins (not straight, but in 10-15 sec spurts with breaks in between). The next day when it was barely above freezing, it started after about 5-10 secs of cranking it, then I drove it about 60 miles round trip and it drove like garbage. It would barely move itself unless I floored it, then it would take off, which was scarey considering I was driving in snow and freezing rain, lol.

Would the O2 sensors cause it to keep from starting and the other acceleration issue? I'm about to go switch the sensors around if I can get them out to see if it follows them. It seems like there's only 2 sensors on it, both on the driver/passenger side exhaust at about the same spot on both sides. Of course yt looks like they're going to be a PITA to take off because they're all rusted in. I assume the wire/connector comes off easily after you get the sensor off or how's that work? Hope I can figure it out along the way.

Thanks again!

 

[MrShorty]

Would the O2 sensors cause it to keep from starting

Not likely. The O2 sensors are not involved in starting at all, and even after starting, they take a few minutes to heat up (especially on a cold engine in the winter) enough to become functional.

Are you still getting the same O2 sensor code(s)?

 

[Forder]

Not likely. The O2 sensors are not involved in starting at all, and even after starting, they take a few minutes to heat up (especially on a cold engine in the winter) enough to become functional.

Are you still getting the same O2 sensor code(s)?

Yeah, and I was getting most of the other 17x codes too. Then I also got a code 542 which is "fuel pump circuit open; PCM to motor". Somehow I just overlooked that and just looked it up. That sounds like it could affect starting, eh? Heh. Got any advice to troubleshoot that?

Thanks.

 

[MrShorty]

KOEO 542 or CM 542? A CM 542 without an accompanying KOEO 542 could indicate that the circuit fault in the fuel pump circuit is intermittent. For years I would get an occasional CM 542 or 543 (can't remember which) that I couldn't diagnose until the morning the break in the circuit decided to become permanent enough for me to track it down.

A KOEO 542 should be pretty easy to track down with a wiring diagram and a voltmeter. Simply find the place in the circuit where the voltage drops.

 

[Forder]

Doesn't the KOEO test show CM codes? Not sure what you're asking, but I pulled those codes with the paperclip trick and watching the CEL blink out the codes. I have a Haynes manual with diagrams, but I'll have to go buy a voltmeter. How did you repair the circuit?

Thanks.

 

[MrShorty]

The KOEO test shows both KOEO codes (the first set) and CM codes (the second set). If you need further explanation, review my "notes on pulling EEC-IV codes" thread.

In my case, it turned out to be a bad connection somewhere between the fuse and the relay. A new wire between those two points fixed the problem. But that doesn't seem to be a common failure point on these.

 

[Forder]

The KOEO test shows both KOEO codes (the first set) and CM codes (the second set). If you need further explanation, review my "notes on pulling EEC-IV codes" thread.

In my case, it turned out to be a bad connection somewhere between the fuse and the relay. A new wire between those two points fixed the problem. But that doesn't seem to be a common failure point on these.

Ahh, I got ya. I got 111 for the KOEO code and the 17x codes as CM codes. I did a KOER test today again and got the 542 again along with a 538 ("System did not receive "goose" test - TESTS ") and 167 ("No Throttle Position sensor change in "goose" test (must get at least 25% rotation) - TPS") . It threw those codes right after I did the half-throttle portion of the test, so I'm not sure if they're bogus codes because I didn't do the throttle right or what.

I got a volt meter while I was out today and I plan on playing with it throughout the week after work. What sucks about it is that it's totally inconsistent and it actually runs fine about 90% of the time like it did today when I drove to the parts store to get stuff to fix the window motor bushings. So I'm not sure how I'm going to track down the problem if it's not showing any symptoms of one. Is this what your truck did until that permanent break happened? Whatever is causing it, it's definitely temperature and/or moisture sensitive because it starts and runs rough when it's below freezing out and sometimes after it's rained all night.

My dad suggested I replace the fuel filter since I haven't done that in the last decade I've owned it, lol. He said his '93 F150 (302 ci) did something similar and threw the CEL one time and it was the filter. So I'm going to throw a new one on there this week since it needs it anyways and see what that does.

Thanks again!

 

[Roadrunner777]

I think you have water in your fuel system. Agree, replace filter, also add a bottle of HEET to next fill-up.