Component Tests and General Diagnostics

The ECM on these models includes an adaptive pilot memory circuit which allows the ECM to maintain an average air/fuel mixture in the event of sensor circuit failure.
1. Remove concealment plug from air flow sensor as outlined.
2. Remove plugs from manifold and connect suitable exhaust gas analyzer.
3. Connect tachometer, start engine and run until engine, catalyst and oxygen sensor are at normal operating temperature.
4. Ensure that curb idle speed and CO level is within specifications on underhood emissions sticker. (If sticker is missing or unreadable, CO levels are typically .2% to 1.0% by volume).
If level is too low, check for any possible air leaks between the throttle plate and the air flow meter such as:
a. Oil filler,
b. Dipstick,
c. PCV hoses and connections,
d. Engine covers.
e. Repair as needed.
5. Disconnect vacuum hose from fuel pressure regulator while observing CO level.
6. CO level should be regulated back to specified level after brief rise.
7. Tighten air control screw in air flow meter until lightly seated. Oxygen sensor should regulate CO level back to specified value.
8. Disconnect electrical connector to oxygen sensor and note actual CO value. CO level should rise to approximately 2% by volume.
9. Stop engine, disconnect battery ground cable to clear ECM memory, then reconnect ground cable.
10. Restart engine. CO level should be considerably higher than value noted in step 9.
11. If system fails to operate as outlined, check for malfunction in oxygen sensor or adaptive pilot control circuits.
12. Reconnect pressure regulator hose, adjust CO level to specified value, then reconnect oxygen sensor lead and install new concealment plug in air flow sensor.