Didn't mean to insult you if i did. I wasn't sure if you knew how this system worked, where it actually has manifold runners that physically move to create longer runners. It's not like the ford 4.6 3v or 4v (or 2.0 spi) where they act similar to choke like you were talking about and actually block off one the intake ports.I realise it has nothing to do with the choke, and your above description is correct. He was asking what it is, and that to me is about the simplest way to describe it. A defective IMRC module or as you stated more commonly a broken lever, leads to alot of the same symptoms as a choke being stuck on an old carbureted engine. And Ford does refer to them as a choke pull off. I am not a tech by any means. But I've been in parts for 17 years now and that was my simplest explanation
The runners are controlled by the IMRC (Intake Manifold Runner Control). The system by default is in the "open" mode (short runner position), so when there is something wrong it just stays in the open mode. When it functions properly, the IMRCx puts tension on the cable which rotates the "DSI clip" and pulls the manifold into long runner position. When you hit ~5200RPM it releases tension and drops the manifold into short runner position, which makes the engine note deeper and allows the car to make a little more power as it pulls to redline.Alright so whats happening is the runner is sticking open. The cable is still connected, and nothing is broken. Im thinking maybe there's carbon build up on runners causing them to stick. Any thoughts?