It sounds like the rack limiter screw is run in too
far.Someone may have done you a "favor" trying to
smooth out the warm idle and gotten it too tight.
The screw is at the back of the pump pointing toward
the oil filter housing. It should be adjusted only on a fully warmed engine and backed out until the engine shakes, then tightened until the engine "just" smoothes out.
Regards,
Randy D.