1998 Ford Expedition

Engine Performance problem
1998 Ford Expedition V8 Four Wheel Drive Automatic 150000 miles

I noticed the engines idle was off and rough. I could hear a vacuum leak in the engine compartment. I found a rubber vacuum hose which had been worn and deteriorated located in the rear, right rear of the engine. It is a Y shaped or T shaped hose (cant remember, sorry). It is not a PCV Valve I believe. It is difficult to get to as it is in a very tight location. I want to replace the problem however I do not know what to call it or how to identify it. I welcome your thoughts. Thank you
February 11, 2010.

If it is a vacuum hose, just replace the part that is bad. Chances are the part is good that it is attached to.

Let me know. Also, if you could get a picture of it and upload it for me to see, it would help. Let me know what size V8 it is.