8.1 Litre Problems

[electricjohn]

Rolodex's last visit here was 5 years ago.

[justgary]

14 minutes ago, electricjohn said:

Rolodex's last visit here was 5 years ago.

But it might help if we actually tag him: @Rolodex

@filftwalton had a similar issue with idle flare in his 5.7L.  He tried everything and got very frustrated with it.  The solution was a (second) new ignition control module under the cap.  It seems that the spark timing was changing enough to affect the idle speed, but it wasn't really noticeable until you loaded or unloaded the engine by shifting in and out of gear.  It could have been a cruddy connection at the pickup coil the whole time, and maybe it got cleaned and reseated during the second ICM swap.  It has been solid for a few years now, so it's definitely fixed.

As for the current problem, I would put a timing light on it and see if the spark is stable.  I would also make sure the throttle body is clean inside before throwing any parts at it.