Had some similar problems with my 2.3l, think it was involving the idle sensor on the transmission which senses whether the truck was still in motion. either way, if you need any info on it, i have the oem schematics if yours is efi.
5.0 (306) from worn out gt mustang
Exploder 31 spline tracloc,linelockin 3:55 rear w/discs
S & R Customs in the works...