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Check Engine Light: P0171 & P0174


purehypeballer

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edmonton, alberta
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these are the codes i was given by the shop!

any idea what to do to solve them??!?!!?

P0171 - system too lean B1
P0174 - system too lean B2

that and i am getting TERRIBLE GAS MILAGES.

this thing is killing me!

joel
 


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mesa 33

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The air/fuel ratio is to rich if thats helps at all but i have no idea how to solve that. i think the ratio is 14.7:1. Your o2 sensors might be bad. But i dont know.
 
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scucci

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Both banks too lean - sounds like intake manifold gaskets.
 




Blee1099

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It could be the 02 sensors.. They typically only have a life span of about 40-60K miles. So if they are original, chances are they are bad.
 




TheJMan

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The first thing to do is check for vacuum leaks. If there aren't any leaks, clean the filaments on the Mass Air Flow sensor (MAF). If they are dirty, the computer won't receive the correct readings and will inject the wrong amount of fuel into the cylinders, which might be why you are getting poor mileage. It might also be a good time to do a good SeaFoam treatment or take it to a shop to have it done if you are not comfortable doing it yourself. Also don't forget to check your air filter, replace it if necessary.

Don't replace the O2 sensors until you have exhausted all other possibilities.
 




gjw02

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Ford extended the warranty in a tsb (#00M12) which addressed the intake O-Rings for an additional 3 years and 36,000 miles. My 2000 XLT was covered when I had it taken care of. I had the same error codes and it would run rough on a cold morning until the O-Rings would expand with heat.
 




KC's Ford

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I am having the same problem with the hard start up while cold.I replaced the IAC myself and cleared the codes.Code 171&174 keeps returning.Not much help with the idle when cold just a little better.The TSB 00m12 has my interest.My 99 4.0 SOHC has 42K on it and it just turner 6 years 20 days ago.I will be calling the Ford Dealer in the AM to see if they will fix this.I did talk to the wrench durning the summer about the rattle from the cam idler but and he told me about the TSB.But he didn't tell me about the intake gasket or the o-ring leak and the hard starts durning the winter.I will post my results once I talke to the Dealer.
 




Howard

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I had similar codes and a slight rattle on my 98 sohc. I did the oom12 kit myself and all the problems are cured.
 




mikkibtune

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P0171 P0174 - My sad story- LOL - Any help out there ?

1998 Ford Explorer XLT 4.0 OHV


Got the P0171 and P0174 codes - wouldnt pass NYS Inspection.

1. Took it to Advance Auto - THEY looked it up and said O2 sensors for sure...
Found two Bosch direct fits - installed codes went away for 45 miles- then back
Still didnt pass inspection.

2. Took it to MIDAS - they tested with their machines and said it needed plenum gaskets - go to Ford and buy em and we'll install em- cheap. Went to Ford - got to Midas and they performed leak tests - said there wasnt an air leak - MUST be dirty fuel system & bad IAC. They did a fuel system cleaning and changed my IAC with one the manager just happened to have in his tool box. Too bad the IAC was for an SOHC. ( I found this out from the Ford PArts dept after the manager called him and the parts guy said the one he was putting in was the wrong part ) - yeah, I knew him .

3. Next stop was the Ford dealer - they looked at it, checked for vacuum leaks, found none, checked all intake no leaks they said, then they cleaned every waking inch of the MAF .Found it was the wrong IAC - cleaned my old one and put it back in. They did another computer diag and all was within normal limits. This solved the problem LONG enough for it to pass inspection ...LOL -- did I mention I used to be a lube tech there ? LOL

----- Of course within 50 miles the check engine light came on again.


So now I have invested all this time, a**ache and money into this and yet the check engine light is still on. I now have a slow coolant leak started at the mid - back section under my engine after having midas also do a flush and fill and replace the thermostat. ( which was malfunctioning and leaking out of the thermostat housing gasket before. )
And it isnt blowing smoke or anything that would lead me to suspect head gaskets ...

Thats about all the relevant information I have - any ideas ?


Thanks,

Mikki
 




Runnin'OnEmpty

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My guess would be intake manifold gasket leaks.

This is a very common problem, and the fix is to install
new gaskets.
 




mikkibtune

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My guess would be intake manifold gasket leaks.

Unfortunately, both Midas and the ford dealer did tests to determine if the intake manifold gaskets were bad and both said they checked out fine.
 




ExplorerDMB

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Check for another vaccum leak somewhere. Also, how did they test it?

-Drew
 




mikkibtune

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The rest of the saga 98 Ford Explorer XLT OHV

Yeah- see I originally brought it in to both places asking them to change my lower intake gasket and plenum gaskets ... after reading all the posts here and doing everything up to that point ... but NOOOOOOO.... of course I was WRONG and they were right ... they've just charged me almost 200.00 at New Country Ford in Saratoga Springs NY to do all this DIAGNOSTIC work on an item where I pretty much KNEW what was wrong, even bought all the OEM Ford gaskets at New Country in advance and everything...but they told me the intake wasnt the problem .... Since then Ive returned the parts to the parts department, been charged a RE-STOCKING FEE, losing 20.00.

Today I called them to ask for credit toward a intake gasket job there since they misdiagnosed my presenting problem and then I had to listen to this loudmouth service advisor tell me how there was no telling WHY the coolant was leaking... and that THERE was NO WAY that COOLANT EVER goes into the channels in the intake at all whatsoever... so it couldnt be the intake manifold gaskets that I originally brought the Explorer in to be changed on...

I let him know I used to be a lube etc technician for Ford.... and worked THERE at New Country as a technician, and then I told him that coolant most certainly DOES flow through the lower intake through channels to cool the intake by FORD DESIGN... and that I was dropping the vehicle off Monday morning and expected to have some resolution to the bogus hours charge... It said right on the repair order that this guy Frank typed himself.... that I requested the lower and upper intake gaskets be changed and that I already had them... How dumb does this guy think I am ??? LOL


I guess we'll see on Monday..... wish me luck guys...
 




ExplorerDMB

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dealership people for you :confused:
 




dcorwin822

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these are the codes i was given by the shop!

any idea what to do to solve them??!?!!?

P0171 - system too lean B1
P0174 - system too lean B2

that and i am getting TERRIBLE GAS MILAGES.

this thing is killing me!

joel


Check your maf and clean it. Its one of the likely causes. what happens is the O2s will read lean because the motor isin't reading the MAF correctly. therefor the engien is dumping a shit ton of gas into the motor making ur long term fuel tirms go thru the roof. hook up a scanner and you'll see that :)

Compare it to the diagrams in the service book to make sure the maf is reading correctly. If not clean it with some residue free cleaner. DO NOT use a q tip its a really sensitive electronic piece!
 




MetallicaRedneck

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I am having these same problems as well with mine, along with a coding stating MAF circuitry low or something. Do you think i need a new MAF? ( i tried buying a used one from a salvage yard, but it didnt have the built in IAT sensor like my MAF sensor, and actually made it run worse. So i put the old one back on.). With all the miles on mine i know it could be a variety of things.
 
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jah81592

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Guys,
A po171 & 174 is a system bank 1 & 2 lean. This is not the O2 sensors. The reason behind this is the o2's are trying to correct but the engine is lean beyond the acceptible correction limits. How do you correct? First as stated in a above post check for vac leaks. In the sohc the intake manifold gaskets are the primary culprit. They are cheap around $20.00 and easy to replace. The stockers are known to fail as I have replaced many different sets on customer cars. Replace them as it is good insurance. Secondly, check for any vac leaks between the maf sensor and the intake manifold. Hoses, clamps and etc. If you have any more questions feel free to email. Thanks-James
 




BonesDT

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Convert to a carb and steal a VIN tag from a pre-80's junker.

Speaking of illegal activities, I wonder why no one has designed a dummy OBD port, that tells any inspection station that everything is AOK.

btw, I just toss a c-note to a shade-tree inspection station every year. it ends up being cheaper than paying for fixes to guessed problems and multiple inspections.
 






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chrisfranco90

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im going thro the same thing right now its not o2 sensors. po171 po 174 are your intake gaskets! replace them and do you spark plugs while your down there....good luck!
 




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