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Oxygen sensor bad?

kgihemp

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I am having a similar problem. Was having a problem with the cel comming on when the motor was under a big load (going up hills, driving 65 on the freeway, excellerating etc.). Then it started to idel rough. I changed out the plugs, wires, pcv valve, and fuel filter. The only thing i found was my #5 plug had the hook portion completely bent out, and the point of the plug was gone. The truck ran better, after I drove it up the hills, and on the freeway the CEL is back. It only comes on after the truck is warm and under a load. When i drive on flat ground the light goes off, but comes back on after a load. When it idles after it is warm it is rough and you can here what sounds like it is "missing". It also smells rich. I have not have the code read, for i live in Germany in the USAF, and it a bit pricey. My friend has a code reader and a few months ago it said "injector pulse switch." Not sure what that is, maybe a FPR. Is there any way to read the codes without a reader. Any ideas on anything?

Hemp
 
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MrShorty

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I can't find anywhere a code for "injector pulse switch." There are a couple for "injector pulse width longer/shorter than expected," which are fuel control related codes.

As for how to pull codes, see the stickies at the top of the EEC-IV forum. Between the two, you should have everything you need to get the trouble codes.
 
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Mud Bug 94

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Dirty Maf Sensor!!!!!
 
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1RadCJ5

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Well today was a nice day in Maine.I decided to tinker a bit to see if I could find any more info.I unhooked the IAC sensor and when I started it, it ran like crap.Much worse than before, didn't wanna stay running at all.I then unhooked my MAF sensor.When I started it, it ran like a new truck.The CEL went on right away instead of after 10-15 mins of driving, due to the fact that it was unhooked.I'm assuming the computer is using stored parameters for it for now.Idles perfect, doesn't seem sooty anymore, and it definately has way more power now.I took it down the road a few miles, and it never ever burned a tire like it does now.Very noticeable! Now the question is, is it really the MAF sensor?? Maybe it was sending a bad signal???
 
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Mud Bug 94

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did you clean it or just unplug the maf?
 
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1RadCJ5

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Hi Mud Bug- I just unplugged it.The only way you would ever know anything was wrong is because of the CEL.I'm not yet sure if my fuel mileage is better, but Hopefully I'll know by the end of the day, as I'm running it up the pike 40 miles.If my tanks empty, guess the mileage is still off, lol.Truck is peppy as all hell now, never was it this snappy.I took the MAF apart a few months back.It appeared clean inside, so I put it back on.Seems like the culprit of a lot of problems here on the board. Mike
 
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Mud Bug 94

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yea i dont know how or why they gum up but they all do eventually.
 
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mikeinri

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I'll say this as gently as I can...

I don't think "I took the MAF apart and it looked clean inside" is a substitute for taking it apart and actually cleaning the element regardless of how clean it looks inside.

The element is the critical part that needs to be clean. Granted, if you have crap in the housing, that will lead to the element getting dirty, but at this point, I think you need to follow the procedure to clean the element to completely rule out this problem.

Also, there is a specific troubleshooting procedure for this problem that you can get at AutoZone (if you know the code number). It tells you the correct voltage ranges on each of the wires to help you figure out if the sensor is really bad.

Which reminds me, check the plastic retaining tabs on the wiring harness connector. Mine is broken, and it made an intermittent failure/ MAF code. I zip-tied it in place, it's been fine ever since.

Good luck, keep us posted.

Mike
 
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kgihemp

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I cleaned my MAF the other day. All problems are gone. I guess every couple of months I will take 5 min and give it a cleaning.
 
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1RadCJ5

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Well I put in another MAF sensor today.No better than before.It actually runs better with it unplugged.Fuel mileage still in the toilet too.I dunno what else to check.The fuel pressure is good, no leaking injectors.Maybe the actual computer? It takes about 8-10 mins before the CEL comes on, I am not sure what to do next.Any ideas or suggestions?
 
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Mud Bug 94

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throttle position sensor?
 
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glfredrick

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Well I put in another MAF sensor today.No better than before.It actually runs better with it unplugged.Fuel mileage still in the toilet too.I dunno what else to check.The fuel pressure is good, no leaking injectors.Maybe the actual computer? It takes about 8-10 mins before the CEL comes on, I am not sure what to do next.Any ideas or suggestions?

With the MAF sensor unplugged, your computer defaults to "open loop" status, which will just send a mapped fuel/spark curve into your engine. It may run OK and even have more power, but it will be running rich, and eventually plug your cats, leading to another problem.

I recommend using something more substantial than a code reader to figure out your problem. Find someone with a Modis or other similar unit that can actually scope your engine while running. Check the spark raster against the MAF and O2 sensor curves to see if they are part of the problem or if it is something else.

You need to find real time data, not just stored codes.

I'd also check the fuel trim to see if it is compensating for some other condition, hence the lack of power when the MAF is connected. Your computer will eventually "learn" what it takes to keep your engine within the maps programmed in, and it will adjust fuel trim (add or subtract fuel amount) to the engine in order to do so. There are two fuel trim settings - one is the minor setting, keeps the fuel curve within specs, the other is the major setting, sets the parameters for the curve. If the major setting is out of wack, the computer is attempting to correct a problem.

Note also that any reading that is out of specs MAY be a bad sensor or MAY be a problem that a good sensor is just reading and attempting to recover via adjustment in the PCM.

One last thought -- and I've seen this a time or two... Have you replaced your alternator or fuel pump recently? If so, what sort of parts did you use? The Zone is notorious for having "dirty" signals sent from their alternators and fuel pumps that totally screw up the computer. New doesn't always mean "good." Keep that in mind. I've also seen similar issues with bad grounds. Once, a bad battery cable caused a CEL that would not go away. The "wiggle test" quickly diagnosed the problem, but not until after a couple of techs replaced almost every sensor and even the PCM...
 
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greyboxer

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Wow guys, just wanted to thank everyone for their input on this, gave me some ideas. Mine(93 XLT 4.0 pushrod, auto) is doing the exact same thing with the on again off again CEL, running rich and all the soot. I ran the codes on mine and also came back w/faulty O2 sensor although I'm not convinced and haven't changed it yet. I changed my vacuum lines, plugs, PCV, and cut about 2" back on my battery cables and put new clamps on. Now it runs great, lot's of jam, shifts smooth, and no soot, but it still reeks to high heaven, the CEL still comes on and off and I get maybe 110 miles(180 km) to a full tank. So if anyone does hit on the fix, as our issues seem identical, post it up and I'll follow your lead! Thanks again.
Gary
 
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mikeinri

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greyboxer...

You're reading the posts, but only implementing half of the ideas. Not to mention, you're grasping at straws (part-swapping without real diagnosis), so I'm not remotely surprised you're still having problems.

You need to check the codes before you do anything else. Otherwise, you're wasting money and time.

If you want to keep tinkering blindly, a freebie fix that can't hurt anything is cleaning the MAF element. It's your free time, not ours...

Mike
 
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greyboxer

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Geez Mike, relax a little. I did pull the codes and although I don't have them in front of me, the only active codes related to O2 sensor. My kudos to all was not intended as a slight to anyone but it seems you interpreted it as such. As the posts have said, the codes may come but might relate to something further up the line causing the sensor to send the code, not necessarily the sensor itself. But thanks for coming out and using some of your "free time" to respond.
Gary
 
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mikeinri

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Hi Gary,

I wasn't slighted in the least. Sorry my sarcasm seemed a bit dry last night. I was only trying to help, or else I wouldn't have spent the "free time" to make a post. (Note: that was another attempt at humor.) :)

Anyway, I looked and didn't see a previous post by you indicating codes. I apologize if I jumped to the conclusion that you saw someone with a similar issue and assumed you had the same problem. People do that all the time here, and end up wasting lots of time and money on the wrong fix. I was hoping we could help you avoid that.

The big thing that was missing in your post to help us help you is, did you clear the codes after each attempted fix, and read them again when the CEL returned? You may be getting a different code now (unlikely but possible).

Also, I didn't see that you attempted to clean the MAF. That's an extremely common problem that is hard to detect (may not be dirty enough to throw a MAF code, but may be dirty enough to affect the engine performance and cause O2 or other codes). It is also free and easy to fix.

O2 codes are quite frustrating. Good luck and keep us posted.

Mike
 
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glfredrick

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FYI, sometimes it actually IS a bad O2 sensor... :D

Especially when you start having the bad fuel mileage issues as greyboxer indicated.

It is just good to know that it isn't always what the Zone says when they pull your codes. Do some more investigative work first - remember, they're in business to sell you parts... not to diagnose cars.

I've watched as even trained technicians make serious parts replacement errors. I've been through hours and hours of Snap On training seminars for using their Modis, Vantage Pro, and other scanners. The scanner can only tell you what the car computer is saying -- not even really what it is reading, for sometimes it resorts back to the "map" burned into it, and just spits out that reading, which will lead you astray every time. To diagnose further, you have to actually test the components, which can be done with a GOOD volt-ohm meter that can read a square wave pattern and a good reference to know what that particular sensor is actually supposed to be doing. No scanner can do that task - it takes another tool.
 
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mikeinri

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That's funny glfredrick, sometimes we overlook the obvious...

O2 issues are the PITA that they are because it indeed can be a bad O2 sensor (or wiring). Problem is, most DIY folks (and even Ford dealers, been there) don't have the time, or gear, or knowledge of how to really determine if the O2 sensors are bad, so they often will just replace them (which in itself is not a fun job).

Then, over 50% of the time, the codes don't go away and it's time to go upstream. At least the O2 sensors are eliminated at that point (unless you get a factory defect). :)

Sometimes, you can get more help than you would expect at AutoZone, but usually it's only if the guy behind the counter owns an Explorer himself. They have an excellent feature that involves entering the code into their computer. It has the ability to print a really long, detailed troubleshooting procedure on a register tape. I had this done for a MAF code once, the diag procedure included instructions for checking voltages for each colored wire, etc.

But, overall you're 100% correct. Diagnosing these things correctly with limited part-swapping seems to be more art than science, and more science than many of us (myself included) have the patience to deal with. :eek:

Mike
 
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greyboxer

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Yeah, it probably is just the O2. Here's how the whole drama unfolded:
Back in early January we had a wicked blizzard plow through, worst in 50 years so they say, and the city darn near shut down, including school buses. So I jumped in the ol' Ford and head to the school to rescue my stranded daughter pushing snow the whole way that was easily at or above my bumper. Made the round trip, had a lot of fun doing it. I don't know if this had anything to do with my CEL woes, but they started the next day. The light started coming on going off again, it was running a little rougher than I was used to, running rich, yada yada...
Before I even thought of pulling codes I checked for vac leaks, loose or faulty plug wires, you know- the cheap and easy stuff but it wasn't any of that. So then I take my wifes digital to the garage and ran the KOEO, CM, and KOER, I'm not too proud to admit that there was no way I was going to be able to keep track of what that blinking light was telling me so I taped it with the camera, downloaded it, and counted em out over 2 or 3 viewings.
KOEO=172
CM=172
KOER=111
Also, no matter what I have done to date, the codes have remained the same and yes I did unhook the battery for approx 30 minutes after changes for reset.
According to my trusty Haynes manual 172 = "Heated oxygen sensor indicates lean condition, right side" - My apologies to Haynes if quoting their book is some kind of copyright infringement, please don't sue me.
So right away I'm thinking I should just replace it and all will be well but I kept checking out other posts and it seemed that even though the code indicated the O2 sensor that may not be the case. The only thing that I haven't done, that I think might help is cleaning the MAF. And I haven't done that because there doesn't seem to be a general consensus on the right way to clean it, I've read about 4 different ways and at least 2 contradict each other and I don't want to FUBAR the thing. And I tend to be kind of clutsy.
I think that might help because for a short time I used a K&N filter but stopped when a Ford tech told me that the oil can gum up the MAF, that was about a year ago but... also when I replaced my air filter I found that the nut in the bottom plastic of the filter case had been pushed down and the front of the case wasn't sealed 100% last time I changed. My fault for not noticing.
So at the end of it all, the truck runs better than it did before the light started, the snow next to the tail pipe isn't black anymore if I leave it run for 5 minutes. But it is still rich, stinks like a Jerry can, my mileage is awful and that irritating light is still on and off.
I think that's the whole story sorry for being so wordy on this post and shall I say "touchy" on yesterday's.
Thanks again all,

Gary
 
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glfredrick

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What I've learned is to be VERY systematic and methodical in diagnosing a problem. Most errors that I see in technicians are based on their "thinking" that they know the casue of the problem and heading right to that spot to begin their repairs. Of course, for the pro, time is money, and if he can beat the book a couple of times he might actually make a buck that day.

I work somewhat differently and I've been at if for 35 + years.

I always start with the basics -- every time -- even if it seems obvious that they are all covered. I also operate on a couple of principles that I've learned over my years of doing this sort of work.

1. Start with the battery, wires, fuses, etc. (charging volts is a simple meter test -- wiggle the cables to see if anything blinks)
2. Check fuel supply and PSI (takes only a couple of seconds to snap a guage on a fuel port fitting)
3. Check all fluids
4. Do a check for vacuum leaks - both visual, feel, sound, and guage (I use starting fluid - SPARSELY sprayed around vacuum fittings and areas of known leaks -- like the intake on Explorers)
4. Scan codes
5. Based on codes (or lack of codes) begin a diagnosis based on symptoms.
A. It is probably electrical rather than fuel related
B. It is probably vacuum rather than electrical related
C. After eliminating vacuum and electrical issues, check the fuel system
D. If none of the above turns out anything, start checking for hard-part failure -- rounded cams, bent pushrods, burnt valves, bad rings, etc. This may require disasembly and/or compression - leak-down testing.
6. Begin testing individual components. For this, use a Vantage, a Vantage Pro, or a GOOD VOM that you know how to use. It will need to be digital, need to have square wave capacity, and need to measure milli-amps.
7. Begin replacing bad components and re-test.

The above is typically my routine for diagnosis.

Also know again that NEW parts are not always GOOD parts. Especially with the cheap parts houses in business these days. I've seen so many "new" but bad fuel pumps (oh, they pump, but not anywhere near what is required -- test for this using a Modis or Vantage (Pro). You can actually count the individual stators on pumps with a good scope, and you will soon see if they are bad or not (or made with fewer than the factory spec stators!).

Dirty alternators (as in the power they produce not being even and "clean" - not that they have dirt on the cases) are one of the worst offenders for ECM problems. Your car computer is just like your home computer -- it needs a clean, stable power supply.

Testing individual components consists of "pinning out" (sticking little wires, pins, or probes of some type) into the proper wires or wire connectors that feed that particular sensor, motor, or circut, then reading a test voltage, square wave pattern, or amps draw to see if the part is within specs.

On an O2 sensor, one can check to see if they are reading properly by using either a good scanner (not a code reader) that will actually show real-time data from the computer to see if the O2 sensors are changing as the car warms up, and then if they assume a steady state once it does. Erratic readings indicate that the O2 may indeed be bad. O2 sensors can also be tested by the meter method above.

Tip for changing them... Heat them up (a small propane torch or a micro torch works great) -- and remove them while they are hot. NEVER use penetrating oil like WD 40. That will ruin a good O2 sensor and also will WELD a new one in the bore once it gets hot. Use anti-seize designed for that application only. Get the correct socket for removal - makes all the difference in the world. Don't scrimp here, unless you actually LIKE drilling and re-threading the bung for a new O2 sensor.

Hope all this stuff helps someone out there.

Now if I could only find enough spare money to get my hands on a Snap On Modis... Ultimate diagnosis tool in the world today. I can actually diagnose compression ratios with the scope in the right settings.
 
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