Diagnosis By Symptom Test

The DIAGNOSIS BY SYMPTOM TEST is divided into specific engine sections. Each section will describe testing procedures and codes for that engine. Use appropriate DIAGNOSIS BY SYMPTOM TEST. The CIRCUIT TESTS are common to all engines, unless noted in test procedures.

Use this test procedure ONLY when directed to do so by results of following procedures in the QUICK TEST  or by following the steps in CIRCUIT TESTS  . Follow test procedures carefully.

1. When engine stalls in operation or during SELF-TEST, runs rough or misses, or has an "always rich" or "always lean" condition, perform the following checks:
   • Perform SYSTEM CHECK, ISC Check. Use CIRCUIT TEST SS  , step 1).
   • Check BP sensor, using CIRCUIT TEST H  , step 11).
   • Check Idle Speed Control (ISC), using CIRCUIT TEST Z  , step 1).
   • Check for, and repair, any bad ground or power connections.
   • Check ignition components (cap, rotor, wires, coil and plugs).
   • Check for short to ground, using CIRCUIT TEST V  , step 9).
   • Check basic engine components (valves, cam timing, compression, etc.).
2. When detonation (spark knock) occurs, see CIRCUIT TEST I  , step 1).
3. If on restarts, high idle speeds and 3-5 minutes of detonation occur, go to CIRCUIT TEST I  , step 1).
4. If no fast idle occurs when A/C is turned on, go to CIRCUIT TEST M  , step 1).
5. If gasoline fumes accumulate in engine compartment, go to CIRCUIT TEST Y  , step 1).
6. If shift indicator light is always on or off, go to CIRCUIT TEST FF  , step 1).
7. If A/C does not cut-off under wide open throttle (WOT) conditions, go to CIRCUIT TEST G  , step 1).
8. If vehicle is sluggish or if performance is poor, boost control is not working correctly. Go to CIRCUIT TEST HH  , step 1). Also perform this test if detonation (engine knock) occurs.

Fig 1: Merkur EEC-IV Wiring Diagram