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Auto Repair Troubleshooting Charts - Engine Performance
Get ideas about what your auto is needing to run it's best



Problem Possible Cause Remedy/Repair
Hard starting (Engine cranks normally)
  1. Faulty engine control system component
  2. Faulty fuel pump
  3. Faulty fuel system component
  4. Faulty ignition coil
  5. Improper spark plug gap
  6. Incorrect ignition timing
  7. Incorrect valve timing
  1. Repair or replace as necessary
  2. Replace fuel pump
  3. Repair or replace as necessary
  4. Test and replace as necessary
  5. Adjust gap
  6. Adjust timing
  7. Check valve timing; repair as necessary
Rough idle or stalling
  1. Incorrect curb or fast idle spec
  2. Incorrect ignition timing
  3. Faulty EGR valve operation
  4. Faulty PCV valve air flow
  5. Faulty TAC vacuum motor or valve
  6. Air leak into manifold vacuum
  7. Faulty distributor rotor or cap
  8. Improperly seated valves
  9. Incorrect ignition wiring
  10. Faulty ignition coil
  11. Restricted air vent or idle passages
  12. Restricted air cleaner
  1. Adjust curb or fast idle speed (if possible)
  2. Adjust timing to specification
  3. Test EGR system and replace as necessary
  4. Test PCV valve and replace as necessary
  5. Repair as necessary
  6. Inspect manifold vacuum connections and repair as necessary
  7. Replace rotor or cap (Distributor systems only)
  8. Test cylinder compression, repair as necessary
  9. Inspect wiring and correct as necessary
  10. Test coil and replace as necessary
  11. Clean passages
  12. Clean or replace air cleaner filter element
Faulty low speed operation
  1. Restricted idle air vents and passages
  2. Restricted air cleaner
  3. Faulty spark plugs
  4. Dirty, corroded, or loose igniter secondary circuit wire connections
  5. Faulty ignition coil high voltage wire
  6. Faulty distributor cap
  1. Clean air vents and passages
  2. Clean or replace air cleaner filter element
  3. Clean or replace spark plugs
  4. Clean or tighten secondary circuit wire connections
  5. Replace ignition coil high voltage wire (Distributor systems only)
  6. Replace cap (Distributor systems only)
Faulty acceleration
  1. Incorrect ignition timing
  2. Faulty fuel system component
  3. Faulty spark plug(s)
  4. Improperly seated valves
  5. Faulty ignition coil
  1. Adjust timing
  2. Repair or replace as necessary
  3. Clean or replace spark plug(s)
  4. Test cylinder compression, repair as necessary
  5. Test coil and replace as necessary
Faulty high speed operation
  1. Incorrect ignition timing
  2. Faulty advance mechanism
  3. Low fuel pump volume
  4. Wrong spark plug air gap or wrong plug
  5. Partially restricted exhaust manifold, exhaust pipe, catalytic converter, muffler, or tailpipe
  6. Restricted vacuum passages
  7. Restricted air cleaner
  8. Faulty distributor rotor or cap
  9. Faulty ignition coil
  10. Improperly seated valve(s)
  11. Faulty valve spring(s)
  12. Incorrect valve timing
  13. Intake manifold restricted
  14. Worn distributor shaft
  1. Adjust timing (if possible)
  2. Check advance mechanism and repair as necessary (Distributor systems only)
  3. Replace fuel pump
  4. Adjust air gap or install correct plug
  5. Eliminate restriction
  6. Clean passages
  7. Cleaner or replace filter element as necessary
  8. Replace rotor or cap (Distributor systems only)
  9. Test coil and replace as necessary
  10. Test cylinder compression, repair as necessary
  11. Inspect and test valve spring tension, replace as necessary
  12. Check valve timing and repair as necessary
  13. Remove restriction or replace manifold
  14. Replace shaft (Distributor systems only)
Misfire at all speeds
  1. Faulty spark plug(s)
  2. Faulty spark plug wire(s)
  3. Faulty distributor cap or rotor
  4. Faulty ignition coil
  5. Primary ignition circuit shorted or open intermittently
  6. Improperly seated valve(s)
  7. Faulty hydraulic tappet(s)
  8. Faulty valve spring(s)
  9. Worn camshaft lobes
  10. Air leak into manifold
  11. Fuel pump volume or pressure low
  12. Blown cylinder head gasket
  13. Intake or exhaust manifold passage(s) restricted
  1. Clean or replace spark plug(s)
  2. Replace as necessary
  3. Replace cap or rotor (Distributor systems only)
  4. Test coil and replace as necessary
  5. Troubleshoot primary circuit and repair as necessary
  6. Test cylinder compression, repair as necessary
  7. Clean or replace tappet(s)
  8. Inspect and test valve spring tension, repair as necessary
  9. Replace camshaft
  10. Check manifold vacuum and repair as necessary
  11. Replace fuel pump
  12. Replace gasket
  13. Pass chain through passage(s) and repair as necessary
Power not up to normal
  1. Incorrect ignition timing
  2. Faulty distributor rotor
  3. Incorrect spark plug gap
  4. Faulty fuel pump
  5. Incorrect valve timing
  6. Faulty ignition coil
  7. Faulty ignition wires
  8. Improperly seated valves
  9. Blown cylinder head gasket
  10. Leaking piston rings
  1. Adjust timing
  2. Replace rotor (Distributor systems only)
  3. Adjust gap
  4. Replace fuel pump
  5. Check valve timing and repair as necessary
  6. Test coil and replace as necessary
  7. Test wires and replace as necessary
  8. Test cylinder compression and repair as necessary
  9. Replace gasket
  10. Test compression and repair as necessary
Intake backfire
  1. Improper ignition timing
  2. Defective EGR component
  3. Defective TAC vacuum motor or valve
  1. Adjust timing
  2. Repair as necessary
  3. Repair as necessary
Exhaust backfire
  1. Air leak into manifold vacuum
  2. Faulty air injection diverter valve
  3. Exhaust leak
  1. Check manifold vacuum and repair as necessary
  2. Test diverter valve and replace as necessary
  3. Locate and eliminate leak
Ping or spark knock
  1. Incorrect ignition timing
  2. Distributor advance malfunction
  3. Excessive combustion chamber deposits
  4. Air leak into manifold vacuum
  5. Excessively high compression
  6. Fuel octane rating excessively low
  7. Sharp edges in combustion chamber
  8. EGR valve not functioning properly
  1. Adjust timing
  2. Inspect advance mechanism and repair as necessary (Distributor systems only)
  3. Remove with combustion chamber cleaner
  4. Check manifold vacuum and repair as necessary
  5. Test compression and repair as necessary
  6. Try alternate fuel source
  7. Grind smooth
  8. Test EGR system and replace as necessary
Surging (at cruising to top speeds)
  1. Low fuel pump pressure or volume
  2. Improper PCV valve air flow
  3. Air leak into manifold vacuum
  4. Incorrect spark advance
  5. Restricted fuel filter
  6. Restricted air cleaner
  7. EGR valve not functioning properly
  1. Replace fuel pump
  2. Test PCV valve and replace as necessary
  3. Check manifold vacuum and repair as necessary
  4. Test and replace as necessary
  5. Replace fuel filter
  6. Clean or replace air cleaner filter element
  7. Test EGR system and replace as necessary




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