Idel problem with my ATX

So this issue was kinda like one that pissdrunx16 is having here.

But its now unique to me, since replacing my IAC did nothing.

So to recap, when I’m at a stop light, the idle drops to 900, then keeps dropping till the car sputters. She doesn’t die, and if I turn on the temp controls the idle shoots to 1,300 or so then drops back down to the problem area. After a bit I get a P0171 CEL. I’ve been checking for vac leaks, though not done with that yet. I’ve made sure the PCV valve is plugged in (the valve itself was replaced like 8k miles ago) and I’ve tried installing a new IAC. I’m about to pull and clean the TB and it was also suggested I look at my crank sensor, thou I have no idea where that is.

My other thought is do I have a fuel sending issue? I mean if the engine is running lean can’t that be caused by a fuel shortage?

Check the vacuum elbow at the rear of the intake manifold where the PCV pipe is attached to the manifold. There is also an accessory vacuum source elbow back there as well. Give it a slight tug to be certain the elbow is not saturated and loose on the nipple. The PCV pipe to manifold elbow will get rotten in time and collapse creating a vacuum leak which may or may not be very audible. If the elbow becomes a blockage (I have seen this twice), then the lack of PCV air is causing the IAC to operate at it’s limit which may not prevent a near stall as well as cause under-reporting of idle air mass from the mass air flow sensor thereby leaning out the idle. Either way, check the elbow…