2000 Windstar Chugging at Idle

My 2000 Windstar (3.8L with 75K miles) is now "chugging" at idle after I made a repair.

About a year ago The engine just ran horribly rough one day and when I opened the hood you could hear the whistle of high pressure air while the engine ran. I don't recall but I'm pretty sure the CEL/MIL light was on. Every shade tree mechanic that looked at it said "blown gasket", OBD ii codes said Bank 2 (I think) running rich. None of the fixes solved it. Bit the bullet and took it to my mechanic. Turns out the metal heater bypass sprung a leak at the welded Y joint. There was no smell of coolant, the engine temp didn't run hot. The whistling noise was the tube sucking air through a finger sized hole! Apparently the PCM adjusted the fuel mix to lower the running temp enough?

A year later my wife pulls into work and calls me with smoke coming out from under the hood. Sure enough it's the same d*** tube! (of course the part was just past warranty.) There was no CEL/MIL and engine wasn't running hot.

I replace the tube, topped off with coolant (with engine running) and after about 2 minutes it slowly stalls. Crank it over again when cool and it starts fine and runs smoothly until the idle drops and then it starts chugging. RPMs go from ~500 to 1000 in a 2 second cycle. It acts like the PCM is revving it when it gets near stall and then drops it back again.

So I wonder, was the PCM still compensating using the pre-fix readings? I drove it a few times - short runs but enough to warm up - to see if it would trigger new settings. After it warms up while driving it's not as severe but it's still bad.

Then I think maybe I'll clear the old codes to trigger a new sensor scan and new hopefully new settings. I don't have an ODB ii, so I pulled the battery cable for awhile. I know this only clears the KAM codes but it was worth a try. No luck. So I swing by AutoZone to "rent" their OBD ii scanner to clear the set codes. THERE WEREN'T ANY!?

The guy suggested maybe clogged injectors or fuel filter and to put in some fuel additive. I figured no harm to try it and drove about twenty miles. No better. GRRRRRRR

Any and all suggestions PLEASE! This van is used alot and I'm at a loss.

If anyone needs more info just let me know. I really need some direction on this soon!

Thanks again

AHAA!

I found that a vacuum tube coming from the firewall was off the engine and when I put it back it runs better, but not perfectly. It still chugs ever so slightly, but it doesn't stall anymore. I must have knocked it off putting the cowling back on? I read that this tube was supposed to have a clamp on it, but mine doesn't. Maybe that's why it fell off?

Anyway the tube is very dry, cracked and brittle and I assume it's leaking just enough to continue the slight chugging. So I want to replace it, but I can't figure what it's called or what exactly it does.

It's a rather large vacuum tube running from a switch/regulator? mounted on the firewall. It connects to the engine just below the IAC, though it doesn't seem to be part of the IAC. I have a Haynes book but there's really no reference to it that I been able to find. Vacuum diagram on the car doesn't really ID it either.

I just need to know what part to ask for at the store or dealership.

Thanks again

You can show it to them at the auto part store...and they will find the correct size line to use.
I don't know what the line is as I am not familiar with the layout on your year.

I found that the hose is the Fuel Vapor Return. After I removed it I found that it's in worse shape than I thought! Is this common after 6-7 years?

I'm still wondering why no CEL or even any codes were set. I drove it five times. Two of these were at least 10 miles. That should have triggered something.

I'll update the results after the part arrives (it wasn't in stock - of course.)