- Diagnosis By Symptom

ENGINE PERFORMANCE CONDITION (ODOR, SURGE, FUEL ECONOMY...) EMISSION SYSTEM CONDITION.


IF THE "CHECK ENGINE" LIGHT IS NOT ON. NORMAL CHECKS THAT WOULD BE PERFORMED ON CARS WITHOUT CLOSED LOOP EMISSION CONTROL SYSTEM SHOULD BE DONE FIRST.


IF GENERATOR OR COOLANT LIGHT IS ON WITH THE "CHECK ENGINE" LIGHT, THEY SHOULD BE DIAGNOSED FIRST.


INSPECT FOR POOR CONNECTIONS AT COOLANT SENSOR. V/C SOLENOID, ETC.. AND POOR OR LOOSE VACUUM HOSES AND CONNECTIONS. REPAIR AS NECESSARY.


^ INTERMITTENT CHECK ENGINE LIGHT BUT NO TROUBLE CODE STORED.


IF FOR ANY REASON ENGINE RPM DROPS BELOW 200, THE CHECK ENGINE LIGHT WILL COME ON UNTIL RPM EXCEEDS 200 AND FOR 4 SEC. AFTER RPM EXCEEDS 200.


^ CHECK FOR INTERMITTENT CONNECTION IN CIRCUIT FROM:


^ DISTRIBUTOR TO ECM TERMINAL "J"


^ BATTERY TO ECM TERMINAL "F"


^ ECM TERMINAL "C" TO ENGINE GROUND


^ ECM TERMINAL "C" TO LAMP DRIVER


^ ECM TERMINAL "D" TO BATTERY (INCLUDING ECM RELAY CIRCUIT)


G LOW BATTERY VOLTAGE (UNDER 9 VOLTS) AT ECM


^ LOSS OF TROUBLE CODE MEMORY MOMENTARILY GROUNDING DWELL LEAD WITH ENGINE IDLING SHOULD GIVE CODE 23 WHICH SHOULD BE RETAINED AFTER ENGINE IS STOPPED AND IGNITION TURNED TO "ON" POSITION. IF VOLTAGE IS PRESENT AT ECM TERM "F" BUT NO CODE IS STORED. ECM IS FAULTY.


^ STALLING, ROUGH IDLE OR IMPROPER IDLE SPEED REFER TO IDLE SPEED ADJUSTMENT PROCEDURE. CHECK - VACUUM CONTROL VALVE


^ DETONATION


CHECK - EGR OPERATION AND VACUUM SWITCH ENRICHMENT CIRCUIT (CHART # 4).


^ SURGE


SEE - IDLE AND WOT SWITCHES ASM. CHECK.


^ POOR PERFORMANCE AND/OR FUEL ECONOMY


SEE - VACUUM CONTROL VALVE CHECK.


^ POOR FULL THROTTLE PERFORMANCE


SEE CHART # 4 - VACUUM SWITCH ENRICHMENT CIRCUIT CHECK. SEE - VACUUM CONTROL VALVE CHECK.


^ ALL OTHER COMMENTS


MAKE "SYSTEM PERFORMANCE CHECK" ON WARM ENGINE (UPPER RADIATOR HOSE HOT).

THE "SYSTEM PERFORMANCE CHECK" SHOULD BE PERFORMED AFTER ANY REPAIRS TO THE "SYSTEM" HAVE BEEN MADE.