Code 47. New 02 Sensors?

[djsk8r33]

really stuck with this one. stumble on acceleration, loss of power sometimes, CRAPPY gas milage, etc, etc

fresh tune up inc plugs wires air/fuel filter. blah blah

i got code 47 from the scanner thats the only code. according to the book its an 02 sensor and running rich

if it IS an 02 senor which one do i replace?
no vac leaks either.

 

[MrShorty]

Haven't ever run across that one. As such, the first thing I would do would be to run down to the library, get the manual out, and study up on what triggers that code and what the diagnostic steps are for it.

Code lists I have access to suggest that the computer is "seeing" a high air:fuel ratio. In addition to possibly being an O2 sensor, I could also see the MAF being involved, maybe the TPS. Possibly fuel delivery related, too. You claim no vacuum leaks, so I guess we'll assume there are no vacuum leaks (though if you feel at all uncertain of that, double check and make sure there isn't a small vacuum leak that you've overlooked). I think the best first step, though, is to find out what triggers that code.

if it IS an 02 senor which one do i replace?

You must be working under the impression that there is more than one O2 sensor. On your '91, there's only one O2 sensor to choose from, so the answer to your question is, "the only O2 sensor in the exhaust stream."

 

[djsk8r33]

Haven't ever run across that one. As such, the first thing I would do would be to run down to the library, get the manual out, and study up on what triggers that code and what the diagnostic steps are for it.

Code lists I have access to suggest that the computer is "seeing" a high air:fuel ratio. In addition to possibly being an O2 sensor, I could also see the MAF being involved, maybe the TPS. Possibly fuel delivery related, too. You claim no vacuum leaks, so I guess we'll assume there are no vacuum leaks (though if you feel at all uncertain of that, double check and make sure there isn't a small vacuum leak that you've overlooked). I think the best first step, though, is to find out what triggers that code.

You must be working under the impression that there is more than one O2 sensor. On your '91, there's only one O2 sensor to choose from, so the answer to your question is, "the only O2 sensor in the exhaust stream."

you are talking about a haynes manual or something on the internet OR the actual library will only have this manual?

i have cleaned the MAF before a few months back with no success, so unless its faulty its fine

ive been everywhere around town and cannot get a fuel pressure test to see how that turns out, as well as trying different gases

i've seen 3 different 02 sensor maps for the 91. just ONE in the exhaust, one before and one after the cat, and also ive seen there is one 02 sensor on each manifold
unless there is more than one but i would only need to replace that one? at autozoo he comes up with 2 different ones, a univeral and an o.e. but doesnt know whether left/right/before/after

 

[camnnikki]

I too own a 91 and over the last month have rebuilt the exhaust from the engine to the tip and can assure you there is only 1 O2 sensor located about 6 inches in front of the cat on the y pipe. There are 2 different sensors, but take my advice and get the o.e. sensor. With the universal you have to wire the sensor yourself, although it is cheaper.

 

[MrShorty]

you are talking about a haynes manual or something on the internet OR the actual library will only have this manual?

I'm talking about a professional "engine driveability and diagnostics" manual. Publishers I've encountered are Mitchell and Motor. Whatever manual it is, it will be specific to your year (or maybe a few different years) and will have detailed "circuit tests" or "pinpoint tests" for each codes (typically that means about 200+ pages for Ford EEC-IV diagnostics). I can't speak nationwide, but most every public library around here has at least a partial collection of auto repair manuals. They are usually in a reference section where they can't be checked out, but you can usually make photocopies of the necessary pages.

 

[djsk8r33]

I'm talking about a professional "engine driveability and diagnostics" manual. Publishers I've encountered are Mitchell and Motor. Whatever manual it is, it will be specific to your year (or maybe a few different years) and will have detailed "circuit tests" or "pinpoint tests" for each codes (typically that means about 200+ pages for Ford EEC-IV diagnostics). I can't speak nationwide, but most every public library around here has at least a partial collection of auto repair manuals. They are usually in a reference section where they can't be checked out, but you can usually make photocopies of the necessary pages.

i've narrowed it down to a FPR or an 02 sensor is there anyway to test either of these for a sure bite

thats if i could find the FPR and the 02 sensor looks almost welded in there. either way might have to bring this to a mech for an hours worth

 

[Alan_V]

Focus on what causes the air/fuel ratio to be rich. Wonky MAF signal, high fuel pressure due to a regulator that won't regulate, engine coolant temp sensor that tells the engine it's reading 100 deg, after you've been running 10 miles, shorted O2 will do it as well On that note, how's the engine temp reading. If the t'stat is stuck open, the engine will run too cold and you can get the same result, rich mixture. Have you stuck a piece of white paper by the tailpipe to see if it turns black?

 

[MrShorty]

i've narrowed it down to a FPR or an 02 sensor is there anyway to test either of these for a sure bite

FPR is tested using a fuel pressure gauge. See the "fuel pressure test mini-diary" in the Under the Hood forum (I think that's where it is).

O2 sensors can be checked with a voltmeter. Look for a signal that varies continuously between 0 and 1 V. You can also check them out of the vehicle using a propane torch. With the sensor element heated in the middle of the flame, the sensor should output ~1V. With the hot sensor in the air, it should read near 0V.

 

[djsk8r33]

Focus on what causes the air/fuel ratio to be rich. Wonky MAF signal, high fuel pressure due to a regulator that won't regulate, engine coolant temp sensor that tells the engine it's reading 100 deg, after you've been running 10 miles, shorted O2 will do it as well On that note, how's the engine temp reading. If the t'stat is stuck open, the engine will run too cold and you can get the same result, rich mixture. Have you stuck a piece of white paper by the tailpipe to see if it turns black?

my hand turned black today when i was tinkering around near the exhaust. this is good correct? (at least im pretty sure it did, i will double check)

temp gauge on dash indicates everything dandy, but the engine is deffinetly not cold, if anything on the warmer side. i could cook my eggs on there!

MAF, FPR, 02 sensor, T-stat - so one of these (hopefully just one) is working inproperly, or not working at all.

MAF is recently cleaned, and i dont think my engine is running cold.
i will test the FPR once i find a fuel pressure guage around here, and the 02 sensorwhen i grab the voltmeter from work