Driver Comment Chart

Driver Comments

Engine Performance Problem (Odor, Surge, Fuel Economy...)

If the check engine light is not on, normal checks that would be performed on the vehicle without the system should be done first.

If the alternator or coolant light is on with the check engine light, they should be diagnosed first.

Inspect for poor connections at coolant sensor, MC solenoid, etc., and poor or loose vacuum hoses and connections. Repair as necessary.

- Intermittent check engine light but no trouble code stored.
- Check for intermittent connection in circuit from:
- Ignition coil to ground and arcing at spark plug wires or plugs.
- ECM voltage supply terminals.
- ECM ground terminals.
- Loss of long term memory. Grounding dwell lead for 10 seconds with test lead ungrounded should give code 23, which should be retained after the engine is stopped and the ignition turned to run position. If it is not, ECM is defective.
- EST wires should be kept away from the spark plug wires, distributor housing, coil and alternator. Wires from ECM terminal 13 to dis. and the shield around EST wires should have a good ground.
- Open diode across A/C compressor clutch.
- Staling, rough idle, dieseling or improper idle stall.
- Detonation (spark knock)
Check: Map or vacuum sensor output.
EGR operation.
TPS enrichment operation.
HEI operation.
- Poor performance and/or fuel economy.
- Poor full throttle performance.
See chart 4 if equipped with TPS. Refer to: Powertrain Management, Computers and Control Systems, Testing and Inspection, Trouble Code Diagnostic Charts, System Check Charts, Chart 4 TPS Enrichment Check, Chart 4 TPS Enrichment Check

- Intermittent no start.
- Incorrect pickup coil or ignition coil.
- Intermittent ground connections on ECM.
- All other complaints
Make system performance test on warm engine. (Upper radiator hose hot).

The system preformance test should be performed after any repairs to the system has been made.