My buddy JUST had the SAME EXACT problems you are describing. It ended up being (and someone please correct the poor terminology) the Idle Control Sensor (maybe Module). I never heard of it. It was not cheap to replace, but it took care of the issue.
07 Acura TL- PHD FB 4.1s for kicks,center, rear fill, AF 1.C TW for dash, AF 8.1 for doors, Audiomobile Elite 2208 for rear deck, Pair of FB 12.1, Helix A4 and saving up for more Helix amps and Bitone.
95 Mustang- DVA-7996;H701/C701; Focal Utopia 3-way on PPI PC2150;Morel M428 on PC2100; Boston TypeM SE tweets on PPI PC225; Sub JL 10W6v2 on PPI PC1400 Special Edition
99 Durango IVA-W505; Memphis: 15-MCS6 x2 sets; 15-MC42; 16-XO3; 15-MCP12D4 x2; Powered by Big Belle 1300