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ODBII codes 0171 and 0174

bcguthrie

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99 Explorer XLT
Need some help really bad. My check engine light has come on and hooked up my ODBII to it. I get the codes 0171 and 0174. I changed my two front O2 sensors and cleaned the MAF sensor and changed my air filter but am still getting the codes. I have been trying to get it smogged. The first time I had it smogged my CO % was 1.23 at 2500 rpm (which falied me) and was told I had a misfire and that was causing it. I changed the plugs/wires and solinoid (spelling) and had it retested my HC (PPM) skyrocketed from 8 (ppm)to 1852 (ppm) at idle and my CO% jumped to 9.08 at idle. Can someone please give me some guidance.
 
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2000StreetRod

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00 Sport FI, 03 Ltd V8
Which engine?

Do you have the SOHC V6? If so, and the upper and lower intake manifold gaskets have never been replaced then they are probably leaking. It is usually worse in cold weather because they shrink with the cold.

Starting my 00M12 Installation
 
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bcguthrie

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Thanks but no I am 99% sure its OHV I remember reading something about xxx in the vin meant it was a OHV vice SOHC
 
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1998Explodasport

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Thanks but no I am 99% sure its OHV I remember reading something about xxx in the vin meant it was a OHV vice SOHC

I believe if the 8th letter in your vin is X you have the OHV and if it's E you have the SOHC.

I think either motor had the intake gasket problem but I could be wrong on that. I just did mine in my SOHC and it wasn't too bad.
 
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1998Explodasport

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Those codes could also mean you're not getting enough fuel however more than likely it's an intake leak or a bad MAF.
 
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gtyates

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Very common on the OHV engine. Over time the upper intake gaskets basically shrink and do not form a tight seal. Had to replace mine as well on the OHV. Also, just a suggetion, but if you have never replaced the camshaft position sensor you might want to consider doing it as well. It is on the backside top of the motor and requires the exact same procedure as replacing the upper intake gaskets so you will save paying labor again if the sensor fails (and it will eventually). In my case the sensor actually failed first and while I was getting it fixed I had them replace the upper intake gaskets.
 
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bcguthrie

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Thanks for the advice.. I changed the MAF sensor and still have both of the codes. Any idea where a link is on how to change the air intake gasket or at least shows me a pic of where it is.

On a side note once the problem is fixed will the chek engine light go off by itself or do I need to erase it?
 
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gtyates

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'09 Sport Trac, '17 Explo
There are several threads on here showing how to change the upper intake gaskets. Procedure is similar for both the OHV and the SOHC engines. Try this thread: http://www.explorerforum.com/forums/showthread.php?t=171819&highlight=intake+gasket

You will probably need to reset the CEL. Simpliest way is to disconnect battery, which you will probably do anyway to replace the gaskets since you do have to unplug a few electrical items in the process.
 
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