The truck: 1999 Ford Ranger 3.slow 4x4
Details: 163,000 miles (less than 9,000 on remanufactured motor)

I bought this from an older gentleman who sunk a lot of money into it. It had issues, and I knew that but the price was right

Upon purchase. Pulled codes and got a few: (p0409 & p1301 or something like that) one was egr, another misfire. Replaced the EGR, IAC, egr hoses. I've cleared the codes, and after about 50 miles of driving I got (p0401). Cleaned the MAF and reset the codes. Inspected lines (or so I thought) and gave it another whirl. 50 miles goes by and now I get the P0174 code (lean bank 2).
Spent some time looking her over a bit more tonight, and found this. Could anyone tell me where this vacuum is "supposed" to go? Could this be the culprit of my hodgepodge of codes? Notice the bolt sticking out of the vacuum line (one of the red lines).

 

Stumped? Anyone with a 3.0 willing to shoot a picture and send it so I can compare where that red vacuum line is supposed to be routed?

 

No vac line routing diagram on the top of the rad core support? Have you looked at the free repair manuals over on autozone.com for one?

For lack of better info, the plugged vac hose is in the approx location of where the vac operated coolant valve is located. Said coolant valve is in one of the coolant hoses leading to the heater core, and when the A/C is put on max there is a vac hose leading to this valve that causes the valve to close, thus stopping coolant from flowing through the core.

I really don't think enough air could leak around that bolt in the pic to cause a lean code. Said another way, the lean code will only show when the condition causing the lean condition is such that the engine management can't overcome it because it's out of range (ie, so lean system can't adequately enrich). And FWIW, misfire codes are in the 0300 series, none of your noted codes are of that nature. For example, P0304 = misfire in cyl 4; another example is p0300 = random misfire, which could be caused by................................................ .................................................. .................................................. .................................................. .......a lean condition.

 

After screwing around with it today some more. The P0174 code has disappeared, but now I'm back to P0402. It surges in rpm's like mad at start up. Levels out after about 1 minute, but that first 30-45 seconds it acts possessed.

CB: I should mention that I did have a misfire code a couple times early in the game. After throwing a few parts at it it hasn't thrown it since. P0301 I believe it was

 

Since the computer is unhappy with exhaust gas recirculation, it suggests that you should have a look at the DPFE sensor, All of its connecting lines, for crimps, dryrot, splits, cracks, poor fit & the feedback orifice under the EGR valve, as if it, or the hose that connects it to the DPFE sensor are clogged with carbon, which an engine that consumes oil can do, it'll mess with the EGR system feedback.

EDIT: WOOOPS for Excessive EGR feedback, P0402, also add the EVR to your suspect list, as if its leaking vacuum, or stuck open, such that its constantly applying vacuum to the EGR diaphragm, it'll cause the EGR valve to remain open & apply exhaust feedback all the time, or if its sticking & slow to close it'll cause mischief. In any case add the EVR to your EGR system suspect list for check out. So, at idle, there shouldn't be any vacuum on the EGR diaphragm vacuum line, if there is, suspect the EVR, or a computer problem thats sending it an opening voltage at idle.

Not familar with vacuum plumbing on the 3.0L Vulcan, so can't offer up a wag on what the plugged vacuum line is for, but it must be close by. It looks like they're running through the firewall into the passenger compartment in the photos, if so, have a look inside to see where they're going. The only thing in there that uses vacuum would be the Heater/AC controls. Are those red lines OEM, or aftermarket????

More thoughts for consideration, keep us posted on your trouble shoot.