I had the codes 0171 and 0174 on 1998 explorer 4.0 liter ohc. Tested MAF, changed pcv and hose, changed egr valve, codes kept coming back. Engine ran pretty good, nothing really noticable as far as idle. But after reading this forum decided must either be fuel pressure low or intake manifold leaking. Tried spraying wd40 around intake manifold gasket and didn't notice any change in rpm or sound, tried once more and found a place where spraying made a difference. Behind the EGR valve ther is a HOLE in the bottom of the plastic throttle body! Anyone have any idea why this would be here? I patched the hole with Bellzona (industrial strength 2 part metal patch) and will see if the code disappears after this. I have photos I would like to attach if I am allowed.
Dave

 

I was not aware that this was a problem with the Ford plastic manifolds. This is not a unknown issue though on plastic intakes, GM has had several revisions of there plastic intake manifold on the 3800 series engines.

Have you checked with Ford on a replacement / upgrade intake manifold?

David

 

I called the dealer and they have the intake manifold for $279, have to order it. I don't know if its an upgrade, probably just replacement. Hopefully the patch will last ok, or I will try to find one out of a salvage yard.
Thanks for your reply,
Dave

 

OUCH! You might check the aftermarket, there are suppliers in the case of the GM 3800, they are about a bill ($100)

David

 

Well the patch seemed to work and the codes are gone seemingly for good now. I don't see any need to replace the manifold at this time, it ought to hold up for another 120k miles as is. Thanks for all the help from this sight.
Dave

 

the only issue i would see with the patch (and im not familiar with the exact product you used) would be heat...I've used JB weld in a pinch before to seal a broken fuel rail (schroder valve broke off in rail) but i wouldnt have trusted it to last as a permenant fix.

i would go junk yard searching but if you're satisfied with it then right on