There is fairly simple way to check the diag codes watching the blinks on the Check Engine light.
Jumper T and E1 on the check connector.
Code 3 and Code 6 will usually give a clue.
The Codes point you in the “trouble areas” - ignitor, ignitor circuit, ECU, or distributor.
In the FSM (1986 Repair Manual - Truck & 4Runner) Pages FI-22 thru 25 will give you the details for diagnostic procedure.
Gnarls.