Engine Controls - Tests W/o Codes: Other Geo Prizm II

HARD STARTING (CRANKS OKAY)

If vehicle cranks okay, but is difficult to start or starts and immediately dies, check the following items

1. Ensure sufficient secondary spark is available.
2. Check distributor cap and spark plug wires.
3. Check spark plugs.
4. Ensure compression is within specifications.
5. Ensure all fuses are okay.
6. Check ignition coil resistance.
7. Check vacuum hoses and switches for no vacuum leaks.
8. Check fuel pump or circuit opening relay.
9. Check fuel pressure.
10. Check for contaminated fuel.
11. Check for faulty in-tank fuel pump check valve, allowing fuel from lines to drain back to tank after engine has stopped.
12. Check EGR valve and solenoid operation.
13. Check air intake system for restriction.
14. Ensure ignition and valve timing are correct.
15. Ensure noise suppressor (if equipped) has correct resistance.
16. Check distributor signal rotor air gap.
17. Check for worn distributor shaft.
18. Check Camshaft Position (CMP) sensor resistance and connections.
19. Check Engine Coolant Temperature (ECT) sensor has correct resistance.
20. Check operation of Idle Air Control (IAC) valve (if equipped).
21. Check Mass Airflow (MAF) sensor.
22. Check Manifold Absolute Pressure (MAP) sensor.
23. Check Throttle Position (TP) sensor.
24. Check for cracks or poor connections at throttle body.
25. Check throttle shaft for sticking and throttle linkage for binding and misadjustment.

ENGINE SURGES AND/OR CHUGGLES

If engine power varies or vehicle feels like it is speeding up and slowing down during steady throttle operation, check the following items

1. Check vacuum hoses for leaks or kinks.
2. Check for proper Torque Converter Clutch (TCC) operation.
3. Check EGR valve and solenoid operation.
4. Ensure correct speedometer operation.
5. Check fuel pressure while condition exists.
6. Check in-line fuel filter and replace if dirty or clogged.
7. Check fuel for water contamination.
8. Determine if condition is caused by a rich or lean system. Using Tech 1, measure O2S/HO2S output voltage while driving vehicle when condition exists. Voltage less than .45 volt, indicates a lean system. Voltage greater than .45 volt, indicates a rich system.
9. Check O2S/HO2S operation and for RTV sealant or silicone contamination. Also check for sensor cracking or glycol contamination. This will cause a false high voltage signal to ECM. ECM will respond by reducing (leaner) air/fuel ratio.
10. Verify ignition timing is correct.
11. Ensure sufficient secondary spark is available.
12. Check ECM ground connections.
13. Check for faulty spark plugs.
14. Check for defective spark plug wires.
15. Check for restricted exhaust.
16. Check charging system output. Repair charging system if voltage is not 12-16 volts.

LACK OF POWER, SLUGGISH OR SPONGY

If engine delivers less power than expected, or if there is little or no increase in speed when accelerator pedal is depressed, check the following items

1. A/C clutch disengages at full throttle (Metro and Tracker).
2. Check throttle cable adjustment.
3. Verify air intake or exhaust system is not restricted.
4. Check for contaminated fuel.
5. Check fuel pressure.
6. Check in-line fuel filter and replace if dirty or clogged.
7. Ensure sufficient secondary spark exists.
8. Ensure ignition timing and controls are working properly.
9. Check ECM ground connections.
10. Check EGR valve and solenoid operation.
11. Determine if condition is caused by a rich or lean system. Using Tech 1, measure O2S/HO2S output voltage while driving vehicle when condition exists. Voltage less than .45 volt, indicates a lean system. Voltage greater than .45 volt, indicates a rich system.
12. Check O2S/HO2S operation and for RTV sealant or silicone contamination. Also check for sensor cracking or glycol contamination. This will cause a false high voltage signal to ECM. ECM will respond by reducing (leaner) air/fuel ratio.
13. Check charging system output. Repair charging system if voltage is not 12-16 volts.
14. Check Torque Converter Clutch (TCC) operation.
15. Check for faulty spark plugs.
16. Check for defective spark plug wires.
17. Ensure valve timing and engine compression are okay.
18. Check for worn camshaft.

DETONATION/SPARK KNOCK

If engine exhibits a mild-to-severe ping or knock (usually worse under acceleration), check the following items

1. Check for contaminated or poor quality fuel.
2. Check fuel pressure.
3. Ensure ignition timing and controls are working properly.
4. Ensure spark plug application and gap is correct.
5. Check EGR valve and solenoid operation.
6. Check PCV valve system operation.
7. Determine if condition is caused by a rich or lean system. Using Tech 1, measure O2S/HO2S output voltage while driving vehicle when condition exists. Voltage less than .45 volt, indicates a lean system. Voltage greater than .45 volt, indicates a rich system.
8. Check O2S/HO2S operation and for RTV sealant or silicone contamination. Also check for sensor cracking or glycol contamination. This will cause a false high voltage signal to ECM. ECM will respond by reducing (leaner) air/fuel ratio.
9. Ensure transaxle/transmission shift points are correct.
10. Check Torque Converter Clutch (TCC) operation.
11. Ensure correct ECM application. Check with dealer for latest application information.
12. Check for engine overheating.
13. Check for restricted air flow or coolant flow through radiator.
14. Check water pump drive belt adjustment.
15. Check for correct thermostat and coolant solution.
16. Check coolant temperature sensor.
17. Check for incorrect or damaged basic engine parts such as camshaft, cylinder heads or pistons.
18. Check for excessive carbon build-up on engine components.
19. Check for excessive oil entering the engine.

HESITATION, SAG OR STUMBLE

If there is a momentary lack of throttle response, which may occur at any speed, or is most severe when moving off from a stop (vehicle stalls), check the following items

1. Check throttle position sensor/switch for sticking or misadjustment.
2. Check Manifold Absolute Pressure (MAP) sensor operation.
3. Check Mass Airflow (MAF) sensor response and accuracy.
4. Check EGR valve and solenoid operation.
5. Check for fouled spark plugs or defective spark plug wires.
6. Check for defective ignition wiring or connections.
7. Ensure ignition timing and controls are working properly.
8. Check charging system output. Repair charging system if voltage is not 12-16 volts.
9. Check fuel pressure.
10. Check fuel for water contamination.
11. Ensure correct ECM application. Check with dealer for latest application information.
12. Check canister purge operation.
13. Ensure engine warms to normal operating temperature.

CUTS OUT, MISSES

If exhaust has a steady spitting sound at idle or low speed. If a steady jerking exists as engine load increases and is not normally felt with engine speed greater than 1500 RPM or vehicle speed greater than 30 MPH, check the following items

1. With engine running and stabilized, using insulated pliers, remove spark plug wires one at a time. If there is about a 50 RPM drop on each cylinder, go to ROUGH, UNSTABLE OR INCORRECT IDLE. If there is no RPM drop or an excessive drop check for spark at suspect cylinder(s).
2. Check for defective spark plugs, spark plug wires, distributor cap or rotor.
3. Ensure spark plug wire resistance is 3000-6700 per foot.
4. Check for defective ignition wiring or connections.
5. Check fuel pressure.
6. Check fuel for water contamination.
7. Ensure fuel injectors driver wiring circuit at each injector is operating.
8. Check valve clearance adjustment.
9. Check for low compression.
10. Ensure valve timing is okay.
11. Check for damaged basic engine parts such as camshaft, valves, pistons etc.
12. Check intake and exhaust manifold passage for casting flash.

ROUGH, UNSTABLE OR INCORRECT IDLE

If engine runs unevenly at idle (may shake) or if idle speed is incorrect or unstable (RPM varies, engine is hunting), check the following items

1. Ensure no vacuum leaks exist.
2. Check PCV valve operation.
3. Check ECM ground connections.
4. Ensure base idle adjustment is correct.
5. Verify vacuum hose routing is correct.
6. Check for defective ignition system components.
7. Ensure ignition timing and controls are working properly.
8. Ensure all fuel injectors are operating correctly and not leaking.
9. Clean fuel injectors.
10. Check for fuel in vacuum hose to fuel pressure regulator.
11. Check for low compression.
12. Check for broken motor mounts.
13. Determine if condition is caused by a rich or lean system. Using Tech 1, measure O2S/HO2S output voltage while driving vehicle when condition exists. Voltage less than .45 volt, indicates a lean system. Voltage greater than .45 volt, indicates a rich system.
14. Check O2S/HO2S operation and for RTV sealant or silicone contamination. Also check for sensor cracking or glycol contamination. This will cause a false high voltage signal to ECM. ECM will respond by reducing (leaner) air/fuel ratio.
15. Check EGR and solenoid operation (There should be no EGR operation at idle).
16. Check air valve, IAC or ISC valve operation.
17. Check MAP sensor operation.
18. Check TP sensor for a sticking throttle shaft or binding throttle linkage.
19. Check charging system output. Repair charging system if voltage is not 12-16 volts.
20. Ensure correct ECM application. Check with dealer for latest application information.
21. Check canister purge and PCV valve operation.
22. Check for A/C signal to ECM when A/C is on.
23. Check park/neutral switch operation.
24. A/C system overcharged, pressure to high or faulty dual pressure switch.
25. Check Engine Coolant Temperature (ECT) sensor.
26. Check Mass Airflow (MAF) sensor.

POOR FUEL ECONOMY

If fuel economy is lower than expected during a road test, or has decreased since previous road tests, check the following items

1. Ensure air intake system is not restricted or leaking.
2. Ensure ignition timing and controls are working properly.
3. Check for faulty spark plugs or spark plug wires.
4. Check for continuous A/C or Defroster operation.
5. Ensure engine warms to normal operating temperature.
6. Check for low compression.
7. Check for restricted exhaust system.
8. Check Torque Converter Clutch (TCC) operation.
9. Check fuel pressure.
10. Check engine coolant level and thermostat operation.
11. Check for proper speedometer calibration.
12. Verify brakes are not dragging.
13. Check for faulty ECM.

EXCESSIVE EXHAUST EMISSIONS

If vehicle fails emission test or has excessive "rotten egg smell", check the following items

1. Check for defective oxygen sensor.
2. Check for proper fuel filler cap.
3. Check fuel pressure.
4. Check for leaking fuel injector if vehicle is running rich.
5. Check canister purge and PCV valve operation.
6. Check throttle position sensor or switch if vehicle is running rich.
7. Check Manifold Absolute Sensor (MAP) if vehicle is running rich.
8. Check EGR operation.
9. Check for vacuum leaks.
10. Ensure ignition timing and controls are working properly.
11. Check for faulty spark plugs or spark plug wires.
12. Check for exhaust leaks.
13. Check for excessive carbon build-up on engine components.
14. Ensure engine warms to normal operating temperature.
15. Ensure correct ECM application. Check with dealer for latest application information.
16. Check for lead contaminated catalytic converter (look for removal of fuel filler neck restrictor).

ENGINE DIESELS, RUN-ON

If engine continues to run after ignition is turned off, check the following items

1. If engine runs smoothly, check ignition switch and adjustment.
2. Check for leaking fuel injectors.
3. Check throttle opener adjustment (Tracker - Federal).
4. Check for excessive fuel additives (high percentage of alcohol).

ENGINE BACKFIRES

If fuel ignites in intake manifold or exhaust system and makes a loud popping noise, check the following items

1. Ensure sufficient secondary spark is available.
2. Ensure ignition timing and controls are working properly.
3. Check for faulty spark plugs, spark plug wires, distributor cap and rotor causing crossfire between spark plugs.
4. Check for proper spark plug wire routing.
5. Check for low compression (sticking or leaking valves).
6. Ensure valve timing is correct.
7. Check fuel pressure.
8. Check EGR and solenoid operation.
9. Check intake and exhaust manifolds for casting flash.

Intermittent Simulation

To reproduce the conditions creating an intermittent fault, use the following methods

1. Lightly vibrate component.
2. Heat component.
3. Wiggle or bend wiring harness.
4. Spray component or wires with water mist.
5. Remove/apply vacuum source.

Monitor circuit/component voltage or resistance while simulating intermittent. If engine is running, monitor for self-diagnostic codes. Use test results to identify a faulty component or circuit.