Check engine light came on about two months ago. I had autozone pull my check engine code and the sales guy there immediately was selling me oxy sensors and spark plugs. My 2002 Ranger (4.0L) has about 110K miles on it, mostly all highway miles. Anyway, I told the autozone guy, not today on the parts, knowing I would check the forums first.

I found this forum and low and behold, the #1 sticky thread is the p0174 code. I pulled the L shaped vacuum hose and inspected it. It looked to be intact, but knowing it was 10+ years old I went back to autozone and got a piece of vacuum hose. I replaced the hose, pulled the battery cable to reset the codes, and have drove it for 2 months. The p0174 has not come back. Yea!!! Thanks guys for saving me some big $$ and hassle of diagnosing what would have been a bitch to figure out. Thanks thanks thanks.