Need help working out reason for codes.

[huntman58]

Hi
Well I am stumped on this on but my thinking is too big of MAF housing. To much air getting to the motor. Possible bad ECU? even the possability of bad injectors. Not sure on any of it just my thinking so far
Truck is a 4.0 OHV. 1993 with out an Egr valve as it is a 49 state fed truck.
I Swiss cheesed the air box and changed the MAF housing to a 70MM (I believe its 70 MM from my measuring) one from a newer ford explorer.
Has a newer Accel coil and also Auto light plugs with good high performance wires also Accel. Also a K and N air filter clean and oiled but not over oiled as I paper towel it over night to make sure.

Truck always had some treble with a ruff ideal and only got 17 MPG with the K and N air filter. its now dropped to about 15 to 16 and after I did get the ideal a bit smother( tightened the upper intake nuts thanks to this sights info) it now went away when in park or neutral or any gear with the A/C on. Has okay power after all it not a 460 LOL. MAF has been cleaned and same with an air idle valve thing on the side of the intake that lets air pass by so it can ideal with the butterfly closed. I did do the butter fly mod also.

Ran codes and this is what I am getting
All pass with KOEO
With KOER I now get 136, 172, 411, and 538.
136 the O2 sensor always lean. And 172 O2 sensor lean
These are real time run codes as they were seen right then by the reader.
the 411 and 538 may be operator fault but not sure as I now I did not goose the throttle during the test and for some reason I kind of remember doing that before .I could not find my manual so winged it a bit but I do know the set up for reading the codes was right just may have forgotten a step to do during the test. the truck will some times show some smoke and when it dose it will also smmell rich . this is more a hot start thing then a cold start . when ricj smelling it also is a very ruff idel and almost wants to die.

I got to fix it on the cheap and make it last for about three more years tell the wife is out of collage has her masters and is working then its sell it or make a play toy from it but for now it is a very needed car for my doctor visits as I am disabled also but can do about 90% of my own work on it but the heavy stuff no motor or tyranny swaps for me.
Any ideas any one?
Thanks ahead of time

 

[Blacksheep Josh]

When you cleaned the valves and such, did you reset everything by disconnecting the battery for about 20 minutes for everything to "be forgotten" and letting the fuel trims be re-figured?

 

[huntman58]

When you cleaned the valves and such, did you reset everything by disconnecting the battery for about 20 minutes for everything to "be forgotten" and letting the fuel trims be re-figured?

Hey Josh I did forget to add that now didn't I but yes I did I make it a habit of disconnecting the battery when ever I work on it as I have been know to forget when I do not do that but just in case I have reset it a few times for good measure also that’s why I am kind of at a loss here

 

[Blacksheep Josh]

Are all sensors plugged in correctly? I only ask because I rode for a week with the MAF not hooked up and couldn't for the life of me figure it out before my 13 year old sister asked "Why isn't that plugged up somewhere?"

 

[huntman58]

That’s a good one and one that can happen being my clips are broken but there zip tied so no way to come out with out cutting them now but hey keep hitting me with things like that who knows maybe I have forgotten some thing. I have also wondered if my injectors may be bad as they have never been replaced and I have tried to clean them but they may be one or two that are worn out. I know they can not last for ever and mine have over 200,000 miles on them now.

 

[MrShorty]

KOER 538 is usually from missing the goose test. If you know you forgot that part, then that's probably where it came from.

My experience with the 411 is that it is not very helpful. It basically indicates that the engine wasn't running smooth.

So we look at the 136/172. The first thing I would ask is if you properly preheated the engine/O2 sensor before running the test? O2 sensors don't function until they are hot. If you aren't certain, take the truck for a short drive immediately before running the KOER test.

If you are still getting these two codes, then a few other things to look at. Do you have a stock MAF housing to put on and check it out? I'm not certain that is the problem, but it might be worth looking at (I'm not even sure what the stock MAF is).

Are you certain the O2 sensors are functional? O2 sensors can be checked with a voltmeter -- especially for gross faults. If you put a voltmeter on it and stays pegged at 0, that's an indicator that the sensor has failed open and needs to be replaced.

Have you checked fuel pressure? "By-the-book" diagnosis of most O2 sensor codes usually starts with a fuel pressure test to make sure the fuel system is functioning properly.

 

[huntman58]

KOER 538 is usually from missing the goose test. If you know you forgot that part, then that's probably where it came from.

My experience with the 411 is that it is not very helpful. It basically indicates that the engine wasn't running smooth.

So we look at the 136/172. The first thing I would ask is if you properly preheated the engine/O2 sensor before running the test? O2 sensors don't function until they are hot. If you aren't certain, take the truck for a short drive immediately before running the KOER test.

If you are still getting these two codes, then a few other things to look at. Do you have a stock MAF housing to put on and check it out? I'm not certain that is the problem, but it might be worth looking at (I'm not even sure what the stock MAF is).

Are you certain the O2 sensors are functional? O2 sensors can be checked with a voltmeter -- especially for gross faults. If you put a voltmeter on it and stays pegged at 0, that's an indicator that the sensor has failed open and needs to be replaced.

Have you checked fuel pressure? "By-the-book" diagnosis of most O2 sensor codes usually starts with a fuel pressure test to make sure the fuel system is functioning properly.

KOER 538 is usually from missing the goose test. If you know you forgot that part = operator problem as I did forget that one

411 we will close our eyes to it for now .

The O2 sensors are functional and were changing readings. The motor was also warmed up good before testing (almost forgot that one LOL)

testing FPR now hmmm some what newer FPR but did not think of that as too high of pressure would or could over fuel it .did check the vac line and no gas there day as a bone but will do a pressure test any way just to cover the bases.
I do have the stock housing for the MAF so will change them out also just to see as ya never know knew there was some reason I held on to that thing besides using it as a paper weight.
thanks MrShorty for the info both you and josh are life savers around here.

 

[huntman58]

Okay changed out the 70MM MAF housing for the stock one drove it for about 70 miles freeway and stop and go after I cleared any codes. So far no stored codes in all of this only codes showing are the KOER test codes.
Codes 172 and 136 again meaning if I am right both banks left and right showing lean all the time. So the ECM is trying to make it richer and that is why the smell of gas and the black soot and smoke now and then

Now once the motor cools off some I plan to do a fuel pressure test both static and running.

No vac leaks that I can find.

Now correct me if I am wrong here but is the IAC sensor used only at idle? I ask because if I do unplug it, it seams to run a bit smother and at lower RPMS. The crazy thing in all of this is under power it runs great it is only at idle were its ruff. now even with that if the A?C is running and its in gear smooth as can be but N or P and its back to ruff but with out A/C its the reveres smooth in P or N and not in gear. I added that just in case it helps any one help me.

Will post the pressure test later to night or first thing in the AM.
Thanks again a head of time.

O ya have cleaned the MAF and the IAC again did that when I changed the MAF housing.

 

[huntman58]

Okay check the fuel pressures and the FPR
Test was
Static pressure = 39 psi
Running w/ vac = 31 psi
Running no vac = 40 psi
5 minute hold = 29 psi (small leak at gage so it may be reason for the small drop)

Haynes manual used and list min and max at ideal as
With Vac = 30 - 45
With out Vac = 40 - 50
Hold after 5 min.= 30 - 40

I could not get a max pump pressure as I do not have a fitting for that test. May have to go to Ace and make one up as the pressures seam to all is on the low side.

 

[MrShorty]

Fuel pressure test looks normal.

Codes 172 and 136 again meaning if I am right both banks left and right showing lean all the time. So the ECM is trying to make it richer and that is why the smell of gas and the black soot and smoke now and then

This suggests to me a fault in the O2 sensor circuits. The o2 sensors are reporting a lean condition when, in fact, the engine appears to be running rich. I would probably be looking at the O2 sensors.

 

[huntman58]

Fuel pressure test looks normal.

This suggests to me a fault in the O2 sensor circuits. The o2 sensors are reporting a lean condition when, in fact, the engine appears to be running rich. I would probably be looking at the O2 sensors.

When I tested them I could see a reading change I was just was I could not use that third hand to gets a reading of what it was I could just see the numbers changing.

Seams strange to have them both go out together as I know there both about two years old. They are both Bosh sensors also. I know the MAF is the OEM one but has been cleaned a few times is it possible that may be also the problem and that it is just worn out from maybe to many miles and or cleanings?

 

[MrShorty]

I'm sure it is possible that the MAF is the cause of your symptoms. If the MAF were at fault, I would expect to see rich O2 sensor codes (173/137) rather than the lean codes. It is the contradiction between the condition of the exhaust (black smoke and gas smell -- rich) and the lean codes that would make me look more closely at the O2 sensors.

 

[huntman58]

Well Mr Shorty playing devils advocate with ya only seams to help your opinion more then mine. So I believe its time to change those suckers out and see what happens as unplugging them and checking out the wiring just to be sure all seams okay so that really only leaves bad O2 sensors any more. good thing about it is I can go back to the 70mm housing also as I have noticed a power drop not much but some when I put the smaller stock one back on. Thanks for your help and I will post an update on this and what I get with a new test once I have new sensors. It may be a bit tell I have the cash but I will take pics of the before during and after replacement incase any one other wants to know were and how to do an O2 replacement on a 1st gen X.

 

[MrShorty]

Since it's going to take a bit before you have the money to replace to O2 sensors, I might tinker with them a little. You said at one point that you put a voltmeter on them and could see a signal out of them, just couldn't see the meter well enough to get numbers. I might try that again. I have seen cases where the O2 sensor is functional (a voltmeter will show the right signal), but a fault inside the PCM prevents the PCM from seeing the signal. I also can't say how many times someone has come on here and reported that the O2 sensor wires got pinched in something or burnt on the exhaust pipe. If you can't immediately replace the sensors, it might be worth the effort to check the wiring and such to make sure it is the sensors that need replaced and not something else in the wiring between the PCM and the sensors or the PCM itself.

 

[BWTGUY]

Check the Idle Air Bypass Valve on the intake manifold. Mine only worked part time and threw the 411 codes all the time.

 

[huntman58]

Since it's going to take a bit before you have the money to replace to O2 sensors, I might tinker with them a little. You said at one point that you put a voltmeter on them and could see a signal out of them, just couldn't see the meter well enough to get numbers. I might try that again. I have seen cases where the O2 sensor is functional (a voltmeter will show the right signal), but a fault inside the PCM prevents the PCM from seeing the signal. I also can't say how many times someone has come on here and reported that the O2 sensor wires got pinched in something or burnt on the exhaust pipe. If you can't immediately replace the sensors, it might be worth the effort to check the wiring and such to make sure it is the sensors that need replaced and not something else in the wiring between the PCM and the sensors or the PCM itself.

Your so right about the pinching or burning part as the first set I put in after the stock one that is just what happened and it took for ever to find them . It was pinched between the motor and bell housing up were you could not see it. Got a connection just not all the time a wiggle finely showed that one then later I did burn a wire when a new pipe was put it. This time did not include any of that as I was thinking may be they or one came loose and some how hit the head pipe. Any way plan to check them out a bit deeper but I also found the money to replace them. E bay is good for some thing after all sold some used fishing stuff and got some good prices for it so my truck found out and now it wants it all just like a kid or wife LOL.

 

[huntman58]

Check the Idle Air Bypass Valve on the intake manifold. Mine only worked part time and threw the 411 codes all the time.

Good idea but no go I even traded it out with a known good one to make sure. But still no change. some what sure its just the sensors at this point but always willing to take a look at other things as that is how we all learn some times .

 

[huntman58]

Well still getting the 411 and now a 412 code along with a 538. All RPM related but not to worried about them as the truck runs and Idles fin all but a very very slight ruff spot now
Do not know what I did but the O2 codes 136 and 172 have gone away. All I did was reclean the MAF again and then put back on the 70MM housing again. I also cleaned and put on a Junk yard AIC vale that clean was still a bit dirtier then mine. No deference in the idle but the codes are gone. drove it for a bit and then retested and still gone so just maybe some how some way recleaning or changing the AIC took care of it with out replacing the O2 sensor. Any way I am happy let hope it stays this way.

Now if I could find away to keep all the plastics from rotting and breaking. O how I wish I had a garage again or at lest a covered parking area as the sun out here in the desert is just baking the Heck out of it!