Wrong Intake Manifold ?

[nitram2]

Recently bought 1998 Explorer, Eddie Bauer, 4.0 SOHC, VIN "E", 130K miles, as my last one had 265K and was showing it.
Check Engine Light came on, reading PO 174, running lean on Bank 2.
Both my mechanic and a Ford specialist could find no evidence of a vacuum
leak, but I decided to replace gaskets as this sounds to be a relatively common problem. That didn't work either so my mechanic ran down the previous owner who admitted to having the same problems and had replaced upper manifold with a manifold off a 2000 Explorer and had rerouted the vacuum hoses because the 2000 manifold was not compatible with the VIS system ! Amazing !
So now what do I do ? Replace both manifolds and add back the VIS components ? Replace just the upper manifold and VIS and hope the problem isn't in the lower ? Or just keep driving with the engine light on until September Emission time ? If the latter, will I do any damage running lean over a period ?
It starts and runs well, but a bit of a gas-guzzler ! Hoses, all sensors and fuel
pressure are all good.
Any suggestions would be much appreciated.

 

[2000StreetRod]

lower intake manifold

I think the 2000 and 1998 lower intake manifolds are identical. Did you replace the gaskets between the heads and the lower intake manifold? Some of those gaskets were leaking on my 2000 Sport. It is difficult to detect the lower gaskets leaking.

The 2000 upper intake manifold without the VIS should work with your 1998 engine. The wire from the PCM to the VIS vacuum solenoid will have nothing to connect to. There should be minimal performance degradation without VIS which is why Ford eliminated it. Many engines rarely exceed 3,000 rpm when the vacuum motor activates the intake runner control.

Bank 2 is the driver side. Here's a link to photos of my 2000 upper intake manifold with a list of the vacuum connections:Intake manifold vacuum lines
You'll have to make sure that the ports are connected to the corresponding 1998 items or the ports are plugged/capped if there is no corresponding item.

 

[nitram2]

Wrong Manifold ?

Thanks for the info which I forwarded to Chris, my mechanic.
He did replace both upper and lower manifold gaskets and is
left scratching his head !
I guess my immediate concern is ongoing damage due to running lean
over an extended time.
Any further thoughts would be much appreciated.
Thanks

 

[Joe Dirt]

Maybe grab the correct intake manifold? They're a dime 'a dozen at junkyards...

 

[ZBlackBeast]

cold maybe the O2 sensor be bad?