Engine Hesitates and/or Poor Acceleration

1. Check clutch and brake for proper operation. If clutch and brake are satisfactory, proceed to step 2. If clutch and/or brake is not satisfactory, repair as required.
2. Check for vacuum leaks in air intake line. If no vacuum leaks are present, proceed to step 3. If vacuum leaks are present, check the following:
a. Hose connections.
b. PCV hoses.
c. Ensure EGR valve stays open.
d. Oil filler cap and oil level gauge.
3. Check air filter. If air filter is satisfactory, proceed to step 4. If air filter is not satisfactory, replace air filter.
4. Access diagnosis codes. If abnormal codes are present, proceed to ``Diagnosis Code Interpretation.'' If normal code is present, proceed to step 5.
5. Check for spark at end of spark plug wire while cranking engine. If spark is present, proceed to step 6. If no spark is present, check the following:
a. Plug wires.
b. High tension wires.
c. Distributor.
d. Ignition coil igniter.
6. Check ignition timing. If timing is satisfactory, proceed to step 7. If timing is not satisfactory, adjust as required.
7. Ensure fuel pressure is as specified. If fuel pressure is satisfactory, proceed to step 8. If fuel pressure is not satisfactory, check the following:
a. Fuel pump.
b. Fuel filter.
c. Fuel pressure regulator.
8. Check fuel injectors for proper operation. If fuel injectors are satisfactory, proceed to step 9. If fuel injectors are not satisfactory, check for injector leakage or damage. Repair or replace as required.
9. Ensure spark plugs are satisfactory. If plugs are satisfactory, proceed to step 10. If plugs are not satisfactory, replace plugs as required and check compression pressure.
10. On models equipped with 2S-E, 3S-FE, 3S-GE, 4A-GE, 4A-GEC, 4A-GEL and 4A-GELC engines, ensure air control valve is open with engine running at 4,350 RPM or more. If valve operates satisfactory, proceed to step 11. If valve does not operate satisfactory, check vacuum solenoid valve for proper operation.
11. On all models, ensure EFI electronic circuit is satisfactory. If circuit is satisfactory, test is complete. If circuit is not satisfactory, check the following:
a. Fusible link, fuse or EFI main relay.
b. Air flow meter.
c. Water thermo sensor.
d. Injection signal circuit.
e. Air temperature sensor.
f. Throttle position sensor.