p1131 and hesitation/stumbling in all speed ranges; high/low o2 sensor voltages

[thegoon543]

i recently have been getting 3 trouble codes; only one of which is a legitimate one:
p1131 - o2 sensor bank lean
p0000
p0000

there is hesitation during idle and across all speed ranges (particularly @ highway speeds). using my ScanGauge II I was able to view the o2 sensor readings and its puzzling me. some days (after it warms up) it can't seem to figure out proper air/fuel mix and appears to "go on strike." one sensor will give me a very high reading (.7v or higher) and the other will read low (.1 or lower). the funny thing is that its never the same o2 sensor going high or low. it usually alternates sensors back and forth after each cold start (typically every day) but still the same symptoms appear.

does this seem to pin down any 1 issue? my semi-educated guess would be that either the EGR and/or DPFE are bad, but my lack of knowledge on the subject would pretty much have me trial and error my way out of it. i just bought an egr from autozone, but they told me if i installed it, i couldn't return it so i'd like to narrow it down if possible.

 

[Cobraguy]

You aren't providing enough information...so I'll try and fill in the blanks.

YOu have 4 O2 sensors. Bank 1 and 2 upstream (the ones you really care about) and bank 1 and 2 downstream. Downstream sensors are only used to verify the efficiency of the catalytic converters. They don't have anything to do with a lean or rich code.

Your code should indicate which bank is lean. In this case, it's Bank 1. Bank 1 is the side where the # 1 spark plug is located...usually the right on these vintage Fords. But I'm concerned about the readings you say you are receiving. Are you certain you are reading the upstream sensors and not the down stream? If you are reading the upstream sensors, something is not right with those readings. O2 sensors create their own voltage signal between 0 and 1 volt. The amount of oxygen in the exhaust determines how much voltage is produced. The sensor creates the proper voltage, sends it to the PCM, the PCM reads it, interprets the data, and corrects the injector pulse width to compensate for a rich or lean condition. This change will change the amount of oxygen in the exhaust and therefore, the voltage reading in the O2 sensor and the whole process starts all over again. This happens several times a second for each side of the engine. The up and down readings from the O2 sensor is called cross counts and should be very rapid. Slow crosscounts are a dead on indication of a tired sensor that should be replaced. Dead solid readings are either dead rich or lean...and the way the car runs would be an obvious indication of that. I would check three things...(1) you were reading the down stream sensors and not the upstream, (2) your scan tool "averages" the O2 readings and cannot display cross counts, (3) You have bad O2 sensors, (4) you have a problem with the truck that is forcing both sensors dead rich or lean. I kind of doubt 3 and 4. But possible I guess. But if you are certain that you are reading the correct sensors and you have a good scan tool (verify cross counts on another vehicle), then 3 and 4 is where I would start looking. If # 4 is valid, you should have a pretty crappy running car.

 

[thegoon543]

my mistake...i only had the two sensors from bank one being read on the scangauge. im going to set it to read the others from bank 2.

ill get back after driving it a little.

 

[Cobraguy]

If you are aren't receiving any cross counts, I suspect you are reading the downstream sensors.

 

[thegoon543]

thanks for correcting me

im able to read all four sensors now after programming the other 2 into my scangauge.

what im noticing (on my drive home today) on the upstream sensors is that the voltage stays higher (at around .7V) on bank 2 about 3/4s of the time. bank 1 will rise briefly to around .7V (for a few seconds) but then quickly drops again, sometimes to zero. it will usually hang around .1 to .2V when bank 2 is high.

im hoping this gives a fairly helpful and accurate picture.

as a test, ive replaced the dpfe sensor (~$55) to see what happens. too early to tell as i had to disconnect the battery to install it, which cleared the trouble codes. the idle seems slightly better, but still seems to have issues above 45mph. im able to take it back but was told if i replace the egr valve that the dpfe should also be replaced at the same time.

 

[Cobraguy]

Both upstream sensors should be rapidly crossing over the .45 threshold. If not, determine why. Do you have a vacuum leak, leaking injector, etc. If you think the vehicle is mechanically sound, then that pretty well leaves you with a lazy O2 sensor that should be replaced. If they have over 50k on them, it wouldn't hurt to replace them as a normal course of maintenance anyway. Even if they aren't bad, they should be getting lazy at that mileage.

 

[thegoon543]

busy

i apologize i have been very busy the past few days and haven't gotten around to giving this attention....hopefully this saturday ill give it more attention

 

[thegoon543]

ok...back to business...my apologies as my holiday season been busy

i checked for vacuum leaks and am pretty confident that my injectors are ok, though i cannot be sure.

i had replaced the dpfe just as a test, but it did little to fix the problem so i was able to take it back.

since my last post, im now pulling a p1132 code in addition to the p1131. from what i gather from other posts this would most likely indicate a bad o2 sensor. i went ahead and bought 2 upstream sensors but have yet to find an empty day to put them in. might as well replace both from what i gather from your earlier post. once i have an update, i will report back.

thanks

 

[thegoon543]

success

replaced both upstream o2 sensors and it everything appears to be back to normal. here is what my old sensors looked like (picture on left shows bank 1 sensor; picture on right shows both: bank 1 and 2 from left to right). i don't know how to tell if they look bad just by the look of them, but my truck runs smooth and no surging or idle hesitation. the codes are still present but i believe they will go away after driving a while. the driver side one was easy to get to, but the passenger side (the one initially giving me problems) was hard due to the tight space where the electrical connector is. neither appeared to have anti-seize compound on them, but they came out pretty easy even with the exhaust cooled down (but not cold). i did put anti-seize on the new ones.

very happy to have this over with. thanks a ton for all the help.

 

[thegoon543]

one quick thing....since ive replaced them, do i need to disconnect the battery to reset the computer? the haynes manual did not indicate whether disconnecting the battery was necessary.

 

[wyochimneysweep]

yeah so the computer can relaern with the new o2 sensors

 

[mrwigglezdj]

very helpful subject , my ole ladies 98 was doing the exact same thing, so now i know what to look at, since auto zone said it was either the mass air flow or o2.
i bought a 98 explorer today for 200 and got the maf off it and put it on hers with nothing changeing leaveing me to belive her problem is the same as yours.

just a little thank you for the helpful information

 

[thegoon543]

yeah so the computer can relaern with the new o2 sensors

thanks for the tip

very helpful subject , my ole ladies 98 was doing the exact same thing, so now i know what to look at, since auto zone said it was either the mass air flow or o2.
i bought a 98 explorer today for 200 and got the maf off it and put it on hers with nothing changeing leaveing me to belive her problem is the same as yours.

just a little thank you for the helpful information

sure....welcome to the site

 

[Cobraguy]

It's not necessary to disconnect the battery as the ECM will relearn on it's own. But it doesn't hurt anything either. If you would rather not lose all your radio presets, clock, etc, just let it learn on it's own or pull the PCM relay and just kill power to the computer.

 

[thegoon543]

i didn't bother resetting the computer, but the codes have cleared and runs great

appreciate the help