Need some intake gasket clarification

My girlfriend has a 97 4.0 Ranger that ran perfectly until it popped a code for insufficient coolant code or something, it was the temp sensor going bad so I replaced the sensor, thermostat, and coolant and all of a sudden the heat was blazing hot like it was supposed to be and the temp gauge actually worked like it was supposed to. However, on the drive home it started idling rough, like it wanted to die, pretty choppy. I ran the codes on it and was getting P0171, and P0174. Eventually I was able to do a carb cleaner test and while it never raised the idle no matter where I sprayed, it did drop/stumble a little when I sprayed it at the front passenger side corner of the plastic upper intake, where it meets the metal lower manifold. I repeated it over and over so that is where the leak is.

Anywho, doing some research (never really worked on a 4.0 Ranger before other than doing plugs/wires and the coolant job), I've found the upper plenum intake gaskets, the set of 3 "D" shaped gaskets connected together. But I've also seen so many people having to replace the fuel rail gasket as well. And while I don't think it looks too difficult, I do need some clarification on the gaskets. On Rock Auto, I found Mahle MS15675A, which is labeled as the upper and lower fuel rail manifold gaskets. It has the 3 "D" shaped gaskets for the upper half, i.e. the upper intake plenum gaskets, but for the lower it shows 2 sets of the beaded paper gaskets. Any clue as to why it includes 2 of the paper gaskets? Because in every picture I've seen, it looks like you just use the 1, then set the fuel rail on top of it and use the studs to torque it down.



I'm going to stay away from doing the lower intake gaskets and the valve covers for now, as I just need the 2 codes to go away, and the kinda bad idle (reverse especially sucks) so we can pass emissions with it and get the tag renewed.

The gasket makers make one set of gaskets for the 4.0 OHV. The earlier ones with an aluminum intake use one of the pictured gaskets between the fuel rail and the lower intake, and the other between the fuel rail and the upper intake.

You have a later version that has the rubber rings for the upper intake gasket, so you just need to use the one paper one below the fuel rail.

Alright thanks, I kinda figured that's what they were doing but just wasn't sure.

I just did the lower intake gaskets on my 98. I did everything while I was in there including the fuel o ring gaskets. It took me 3 or so hours and that was doing it leisurely at work one Friday evening. It’s not a bad job at all. I had a massive coolant leak at the front of the manifold.

I would suggest doing the entire job. You’re already going to be in there half way.


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