I only replace parts on the Taurus with Motorcraft parts.
That hose to the distribution box is pulling a lot more air when the engine is at idle than the crankcase breather hoses that are part of the PCV
system. Are you saying that hose should have even less vacuum than the breather hoses? Is the box just a box with a bunch of hoses that connect to it or does it have some kind of valve that moves inside? It would seem as though even if it is metered air, bypassing the IAC
solenoid and the throttle would make it difficult for the IAC
solenoid to do its job. But if that's the original design, and the box isn't supposed to restrict the flow, then that's cool I guess.
I'm not experiening high idle, and my LTFTs are only slightly elevated but less than 3%. I actually got the P0171, and P0174 warnings for lean mix the other day. I replaced the hose from the PCV
valve to the IM (which I did previously 5 years ago) and the PCV
valve itself while I had the hose off (which I replaced 2 years ago), (all parts Motorcraft), I cleared the DTCs and the PCM
hasn't stored any codes since I did this (several days, several drive cycles, and over 200 miles). However it does seem to idle a bit rough and the RPMs dip close to around 500 at times and I'm trying to figure out why.
I had the dealership replace my harmonic balancer a few months ago because I just didn't have the time. I also had them replace the front seal while they had the balancer off. I'm wondering if the rough idle is from something they did, me being paranoid thay they messed up and noticing things I didn't notice before, or just that the car is getting old and engine parts are getting worn (193K).