1997 ram 1500, 4x4, 408, NV 4500.
As the title says, I'm having issues with hanging idle. This started a few months ago intermittently. To begin with, it would only show when logging a tune for Ryan, and only on occasion. As we progressed with the tune it became more consistent... Only while running his tune.
Starting around the end of November it started doing it even with the original tune I started with (Hemifever canned 91 octane tune), and the factory tune.
Once I realized it wasn't a glitch in the tune causing it I started looking for vacuum leaks, or anything I could think of that might cause it. New IAC (MOPAR)-no change, new TPS (MOPAR)-no change, cap all vacuum lines (except MAP)-no change, and of course go over the intake thoroughly.
The only good(?) thing is how consistent it is. Whether coming down from driving, or blipping the throttle from idle. It will hang at 1700 rpms for 1 or 2 seconds, then 1200 rpms for 7 to 10 seconds. Then it will fall smoothly to where it's supposed to be (750). The only vacuum stuff running on this truck is climate control and brake booster. The previous motor had vacuum issues, so I eliminated everything else.
Anyone want to bounce some ideas my way on this? I'm at a loss. It has done the same with 3 IAC's (good functioning from previous motor, new Napa, new MOPAR) 3 TPS's (same as IAC), and 3 MAP's (same also).
Thanks for reading my novelette.