2005 4.0L Intake Vacuum Leak | Ford Explorer Forums - Serious Explorations

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2005 4.0L Intake Vacuum Leak

yazuki101

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January 17, 2014
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Year, Model & Trim Level
2005 Explorer Sport Trac
Hello,

I am having problems diagnosing the cause of the error codes my truck ('05 Sport Trac) is throwing, P0171 and P0174. I know that the problem is un-metered air creating a lean condition. I have recently replaced the entire PCV assembly, including the tubes and both elbow joints (within a year). I tried using WD-40 to see if I could get the RPMs to spike from a vacuum leak in the intake manifold. Unfortunately, the idle is fluctuating so badly that I cannot tell if the spikes are from the WD-40 or just the sporadic idle which was already present. So I tried using a stethoscope to pinpoint the leak and I can hear air movement on the drivers' side, when I insert the end of my stethoscope in between the intake manifold and the valve covers. However, I am not sure if the potential leak would be in the upper or lower gaskets.

So basically, my question is whether I should buy both the upper and lower gasket sets, or is there someway to tell which one is the problem (such as a secondary symptom, like perhaps oil would be present if it was the lower gaskets).

Any help would be greatly appreciated, thank you.
 






Use starting fluid. WD-40 flash point is too low. Dave P.
 






Use starting fluid. WD-40 flash point is too low. Dave P.

Thank you for the input. I don't have any starting fluid, but I tried using carb cleaner and MAF cleaner as well. I am assuming their flash points are probably similar to WD-40. I will have to wait until I can grab some before trying.
 






did you ever figure out what the source was? I also have p0171 and p0174 codes on my 4.0L V6 (2002 Explorer XLT).
 






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