The computer sends out a timing advance correction to the ICM over the SPOUT wire and then looks for the change on the IDM wire.
IDM - Ignition Diagnostic Monitor
SPOUT - Spark Output Signal from EEC/PCM
ICM - Ignition Control Module
You might check the ECT or the IAT sensor for your problem.
Also check the SPOUT/IDM wire going to ground.
ECT - Engine Coolant Temperature sensor and it has two wires on it.
IAT - Intake Air Temp
IDM (feedback) is a Dark Green with a Yellow stripe wire on the distributor connector.
IDM is pin 4 on the 60 pin ECM connector.