4.0L OHV & SOHC V6 Tech General discussion of 4.0L OHV and SOHC V6 Ford Ranger engines.

CEL Bank 1 and 2 lean p0171 p0174 HELP PLEASE

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Old 10-05-2009
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CEL Bank 1 and 2 lean p0171 p0174 HELP PLEASE

Hello all. Long time no see.


I need to pass inspection. I have searched and searched. Found possible problems. From what I can figure my problem is some sort of vacuum leak. As that is the most likely problem for those codes both coming up together.

Here is what I have done so far.

Checked all hoses for visual cracks or leaks. Maybe not all hoses but all the ones I could find.
I don't have vacuum hubs any more but those were removed years ago this CEL came on within the last 2 months.
Replaced PCV since it could have been a problem and only cost 3 bucks.
Cleaned MAF.
Cleaned sensor in intake after MAF. (forgot what thats called)
I have also sprayed down the engine bay with brake cleaner and can't seem to find the problem. But I don't necessarily think that rules out vacuum leak.
I have also dumped in a bottle of injector cleaner but doubt the injectors are the problem since the truck runs strong without any hesitation.


Also. My heat/ac doesn't work correctly but hasn't worked correctly for about 3 years. The blend door doesn't always work right. It blows defrost and floor most of the time. If I turn on the 4 low it will blow out the vents and will stay on the vents for 30 minutes then back to the def/floor. I don't drive around in 4 low all the time. I just switch it over then back to 2wd. This problem occured first when i did a cowl snorkel. I know that problem and it has to do with the vacuum canister. I did my best to feel up into the fender and check it and all feels fine. I didn't want to remove the fender if I didn't have to since it is a pain to get back on and I am not sure I will get it back on since it is bent now.

Okay so what course of action should I go with next???

Fuel filter??
Replace intake manifold gasket??
Replace O2 sensors??

Should I pull my plugs and see if they tell me anything? I prolly should replace them anyhow but I suspect this won't get me through inspection.

Thanks in advance.
 
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Old 10-05-2009
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its super easy to find the vacuum leak, just leave your truck idling find the hissing sound an see the collapsed hose which is more than likely going to be the 90 degree bend at the front of your intake manifold, i dont have a picture of it anywmore but go take a second look with the engine running, you should see/hear it
 
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Old 10-05-2009
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ahh you have an OHV.. its probably not the 90 degree part i said
 
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Old 10-06-2009
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two vacuum lines coming out of the throttle body, check em both because they go soft and fall apart. Upper manifold gaskets could also be the problem. Both set off the same codes in my truck.
 
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Old 10-06-2009
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Iv got the same problem and so far have done the same steps as you... no luck so far
 
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Old 10-07-2009
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I checked over the vac lines at the throttle body...I guess I will check them again.

I am also going to replace the fuel filter and see if that fixes it. If that is a no go then I am going with intake gaskets.

Anyone have the part number for the intake gaskets so I don't get the wrong ones from Advance.
 
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Old 10-07-2009
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Intake manifold gaskets are super common, but is the trucking acting up at all? How so?

I ordered mine from rockauto.com , also I was lucky enough that just replacing the upper gaskets did the trick.
 
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Old 10-07-2009
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You can pick up a set of FelPro's at your local autoparts store. I did mine in about two hours.
 
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Old 10-08-2009
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Originally Posted by brianjwilson
Intake manifold gaskets are super common, but is the trucking acting up at all? How so?

I ordered mine from rockauto.com , also I was lucky enough that just replacing the upper gaskets did the trick.

Truck is not acting up at all. Drives and runs just as it has for the last 60,000 miles.
 
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Old 10-08-2009
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Interesting. The explorer started acting up before the codes came. On cold mornings it would run rough when accelerating until it warmed up, couldn't figure out why. Apparently the rubber intake manifold gaskets leaked just a little when cold. As they warmed up they became more pliable and sealed up, ran fine. When the CEL finally came on it made sense.
 
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Old 10-08-2009
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Honestly i would just replace the o2 sensors, i had the same problem and new o2 sensors fixed it. but they are kinda spendy...
 
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Old 10-09-2009
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Originally Posted by paintballer4758
Honestly i would just replace the o2 sensors, i had the same problem and new o2 sensors fixed it. but they are kinda spendy...

I will not spend over $100 when there are several other things that seem more likely that I can fix that don't total $50.

It is a bit foolish to replace O2 sensors first. It doesn't make the most sense since it is unlikely that both O2 sensors would fail at the exact same time. When I first checked the code it was Bank 1 and Bank 2. It's not like one code came up then the other. I checked the code within 2 days of it popping up.

I am not rulling it out all together...just as the last option once I have exhausted all other possibilities.
 
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Old 10-09-2009
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My mom's explorer is throwing one of those codes too. Her's is lean on bank one. I just cleared the code and no more CEL. I know its not the way you want to do it though.

I looked all over her explorer and couldnt find any bad hoses. I believe it might be the o2 sensor on her 4.0L. Lets hope thats not the case on yours.
 
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Old 10-09-2009
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Originally Posted by robert99ranger
My mom's explorer is throwing one of those codes too. Her's is lean on bank one. I just cleared the code and no more CEL. I know its not the way you want to do it though.

I looked all over her explorer and couldnt find any bad hoses. I believe it might be the o2 sensor on her 4.0L. Lets hope thats not the case on yours.
Clearing the code does not mean the problem still doesn't exist. It takes 3 cycles of the engine throwing the same code for the CEL to pop up.

Being that you have only 1 bank lean it makes complete sense that you have 1 bad O2 sensor.
 
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Old 10-10-2009
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since you are having a problem with you vents id say you have a leak some where in the vacume system that runs the vents.
or it could be the intake gaskets.
 
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Old 12-17-2009
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i have the same problen minus the vent problem

i will get the gasket # when i get out of school for you

but my question is dose anyone have the procedure of replacing the gasket? because im running in to a problem getting it off

Thanks
-Andy
 
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Old 12-19-2009
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I had the same two codes two weeks ago. Turned out I had a seal on bottom of my oil cap causing an un-metered air leak behind the MAF which thru the codes. Picked up a new cap and its been fine after clearing codes.

Anytime you get a lean bank 1&2 it has to be a vac leak or a inlet leak somewhere after the MAF.
 
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Old 12-19-2009
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It turned out to be my pcv
 
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Old 12-19-2009
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I have extra authentic brand new ford oxygen sensors cheap if you want them to fix your problem.
 
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Old 12-19-2009
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my mother windstar has the same codes i replaced everything that it could be then i caled my buddy at his shop and told him he said 02 just change them and it will go away so i did and 3 weeks later no light still
 
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Old 12-19-2009
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they will come back on. i cleaned my maff and it did nothing. besides do you think both o2's are just gonna fail at the exact same time? i doubt it.
 
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Old 12-19-2009
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yep i do i have seen it more then once
 
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