GM Service Manual Online
For 1990-2009 cars only
Table 1: Hard Start
Table 2: Lack of Power, Sluggishness, or Sponginess
Table 3: Rough, Unstable, or Incorrect Idle and Stalling
Table 4: Hesitation, Sag, Stumble
Table 5: Surges/Chuggles
Table 6: Detonation/Spark Knock
Table 7: Engine Overheating
Table 8: Poor Fuel Economy

Hard Start

Checks

Actions

Malfunction of Ignition System

  • Faulty fuse

Replace the fuse.

  • Faulty spark plug

Clean and adjust the plug gap or replace.

  • Electric leakage at the high tension cable

Replace the cable.

  • Poor connection of the high tension cable or lead wires

Replace the cable or wires.

  • Improper ignition timing

Adjust the ignition timing.

  • Faulty ignition coil

Replace the ignition coil.

Malfunction of Fuel System

  • Lock of fuel in the fuel tank

Feed the fuel.

  • Dirty or clogged fuel filter

Replace the filter.

  • Clogged fuel pipe

Clean the fuel pipe.

  • Malfunction of the fuel pump

Replace the fuel pump.

  • Malfunction of the fuel injector

Replace the injector.

  • The foreign material in the fuel tank

Clean the fuel tank.

Decline of Compression Pressure

  • Poor tightening spark plug

Tighten to the specified torque. Refer to Fastener Tightening Specifications .

  • Cracked cylinder head gasket

Replace the gasket.

  • Inadequate valve clearance

Adjust the clearance.

  • Leakage of the valve clearance

Repair the valve.

  • Interference of the valve stem

Replace the valve or the valve guide.

  • Low elasticity or damage of the valve spring

Replace the valve spring.

  • Abnormal interference of pistons and cylinders

Replace the piston ring.

  • Excessive wear of pistons, rings, or cylinders

Replace the ring or the piston and boring, or replace the cylinder.

Others

  • Broken timing belt

Replace the belt.

  • Malfunction of positive crankcase ventilation (PCV) valve

Check and replace the PCV valve, if needed.

  • Loosening, damage, or leakage of the vacuum hose

Connect the hose correctly or replace it.

  • Leakage of the intake system

Replace the intake system.

Lack of Power, Sluggishness, or Sponginess

Checks

Actions

Decline of Compression Pressure

Refer to Symptoms - Engine Controls .

Malfunction of Ignition System

  • Improper ignition timing

Adjust the ignition timing.

  • Faulty spark plug

Adjust or replace the spark plug.

  • Electric leakage or poor connection of the high tension cable

Connect the cable correctly or replace it.

Malfunction of Fuel System

  • Clogged fuel pipe

Clean the pipe.

  • Clogged or contaminated fuel filter

Replace the filter.

Others

  • Clogged exhaust system

Check and repair the system.

  • Clogged or contaminated air cleaner element

Clean or replace the air cleaner element.

  • Leak of the intake manifold gasket

Replace the gasket.

  • Dragging brakes

Repair or replace the brakes.

  • Slipping clutch

Adjust or replace the clutch.

Rough, Unstable, or Incorrect Idle and Stalling

Checks

Actions

Decline of Compression Pressure

Refer to Symptoms - Engine Controls .

Malfunction of Fuel System

  • Clogged fuel pipe

Clean the pipe.

  • Clogged or contaminated fuel filter

Replace the filter.

  • Malfunction of the fuel pressure regulator

Replace the regulator.

Malfunction of Ignition System

  • Malfunction of the spark plug

Adjust or replace the spark plug.

  • Electric leakage or poor connection of the high tension cable

Connect the cable correctly or replace it.

  • Poor ignition timing

Adjust the ignition timing.

  • Malfunction of the ignition coil

Replace the ignition coil.

Others

  • Clogged or contaminated air cleaner element

Clean or replace the air cleaner element.

  • Leak of the intake manifold gasket

Replace the gasket.

  • Malfunction of positive crankcase ventilation (PCV) valve

Check the valve or replace it, if needed.

  • Poor connection or damage or leakage of the vacuum hose

Connect the hose correctly or replace it.

Hesitation, Sag, Stumble

Checks

Actions

Decline of Compression Pressure

Refer to Symptoms - Engine Controls .

Malfunction of Ignition System

  • Poor ignition timing

Adjust the ignition timing.

  • Poor spark plug or poor adjustment of the plug gap

Replace the plug or adjust the gap.

  • Electric leakage or poor connection of the high tension cable

Connect the cable correctly or replace it.

Others

  • Malfunction of the air cleaner system

Clean or replace the air cleaner system.

  • Leak of the intake manifold gasket

Replace the gasket.

Surges/Chuggles

Checks

Actions

Decline of Compression Pressure

Refer to Symptoms - Engine Controls .

Malfunction of Fuel System

  • Clogged fuel pipe

Clean the pipe.

  • Clogged or contaminated fuel filter

Replace the filter.

  • Malfunction of the fuel pressure regulator

Replace the fuel pressure regulator.

Malfunction of Ignition System

  • Malfunction of the spark plug

Adjust or replace the spark plug.

  • Electric leakage or poor connection of the high tension cable

Connect the cable correctly or replace it.

  • Poor ignition timing

Adjust the ignition timing.

Others

  • Leak of the intake manifold gasket

Clean or replace the gasket.

  • Leakage of the vacuum hose

Connect the hose correctly or replace it.

Detonation/Spark Knock

Checks

Actions

Overheated Engine

Refer to Engine Overheating .

Malfunction of Ignition System

  • Abnormal spark plug

Replace the spark plug.

  • Poor ignition timing

Adjust the ignition timing.

  • Electric leakage or poor connection of the high tension cable

Connect the cable correctly or replace it.

Malfunction of Fuel System

  • Clogged or contaminated fuel filter and fuel pipe

Clean or replace the fuel filter and the fuel pipe.

Others

  • Leak of the intake manifold gasket

Replace the gasket.

  • Excessive carbon deposit due to abnormal combustion

Remove the carbon.

Engine Overheating

Checks

Actions

Malfunction of Cooling System

  • Lack of coolant

Refill the coolant.

  • Malfunction of the thermostat

Replace the thermostat.

  • Malfunction of the cooling fan

Check or replace the cooling fan.

  • Poor water pump performance

Replace the pump.

  • Clogged or leaky radiator

Clean, repair, or replace the radiator.

Malfunction of Lubrication System

  • Poor engine oil

Replace the engine oil with the specified one.

  • Blocking oil filter or strainer

Clean or replace the oil filter or the strainer.

  • Lack of engine oil

Refill the oil.

  • Poor oil pump performance

Replace or repair the pump.

  • Leakage of oil

Repair the leak.

Other

  • Damaged cylinder head gasket

Replace the gasket.

Poor Fuel Economy

Checks

Actions

Decline of Compression Pressure

Refer to Symptoms - Engine Controls .

Malfunction of Fuel System

  • Leakage of the fuel tank or the fuel pipe

Repair or replace the fuel tank or the fuel pipe.

Malfunction of Ignition System

  • Improper ignition timing

Adjust the ignition timing.

  • Abnormal spark plug - Excessive carbon deposit, inadequate gap, burnt electrode

Replace the plug.

  • Electric leakage or poor connection of the high tension cable

Connect the cable normally or replace it.

Malfunction of Cooling System

  • Malfunction of the thermostat

Replace the thermostat.

Others

  • Improperly installed valve

Repair or replace the valve.

  • Slipping clutch

Repair or replace the clutch.

  • Low pressure of tires

Adjust the pressure of the tires.