misfire when cold -misfire when shifting on 1993 Chevrolet Suburban 2500

no misfire when timing set wire is disconnected. no codes. runs fine if wire is left disconnected after timing is aet but code does ahow. work done so far replace distributor,plugs, wiring,trans wiring and selonoids, all wiring for damage, ecm(2), idle air control,map sensor,EGR gasket. Same problem persists,190k miles.Problem started after vehicle sat for one week

Asked by for the 1993 Chevrolet Suburban 2500
It sounds like you may have a bad engine computer ground. Wiring diagrams available from autozone.com may show where. They could be on the bell housing bolts, the engine block, or on one of the intake manifold bolts. The computer grounds must be clean and tight - make sure they are.
2 answers
Check your timing.