Symptom Related Diagnostic Procedures

After completing the MCU or EEC diagnostic procedure, and tracing the probable cause of the problem to the feedback solenoid, perform one or more of the following procedures:


Feedback Carburetors - Rough Idle, Lean Drive

1. With the engine running at idle, retighten the solenoid mounting screws to 30 lb-in. If idle does not change, proceed to Step 2.


2. With the engine running at idle, apply a stethoscope or metal rod to the solenoid body and listen (or feel) for a 10 Hz constant pulse. If the pulse is not evident, or is erratic, replace the solenoid assembly and gasket.


3. With the engine running at idle, disconnect the solenoid lead. If the idle quality improves significantly with the solenoid disconnected, replace the solenoid assembly and gasket.


NOTE: Since disconnecting the lead will appreciably richen the idle mixture, similar to the propane-gain technique, some degree of idle quality improvement and idle speed gain is to be expected, even with a properly operating solenoid.



Feedback Carburetors - Running Rich, Poor Economy


Use Step 2, above for diagnosis.


NOTE: The 2.3L or 4.9L YFA 1-V Feedback Solenoid for the 1985 model year is not interchangeable with the 1981/82 4.9L solenoid. The former being designed for 38 ohm resistance, while the 1981/82 (4.9L) is 22 ohm. The Electronic Control Assembly (ECA) will be damaged if these units are interchanged.