As I say ck. the wiring, & wiggle & jiggle everything. The Dealership may have the "Proceedures" for a "Rudamentary Test" with an "Ohm Meter", but they usually just test by "Swapping" after they are sure there are no "Bare Wires & Bad Connectors". I would check with Salvage Yards for the Module. 1/2 List is common. Have U had the Dist. pulled apart & looked at? While apart, ck. the bearings applying side to side pressure. If U see or feel movement it may be enough to effect problems of timing & running, especially when starting.   John