| The Problem | Is Caused By | What To Do |
|---|---|---|
| Faulty high speed operation | Incorrect ignition timing | Adjust timing (if possible) |
| Faulty advance mechanism | Check advance mechanism and repair as necessary (Distributor systems only) | |
| Low fuel pump volume | Replace fuel pump | |
| Wrong spark plug air gap or wrong plug | Adjust air gap or install correct plug | |
| Partially restricted exhaust manifold, exhaust pipe, catalytic converter, muffler, or tailpipe | Eliminate restriction | |
| Restricted vacuum passages | Clean passages | |
| Restricted air cleaner | Cleaner or replace filter element as necessary | |
| Faulty distributor rotor or cap | Replace rotor or cap (Distributor systems only) | |
| Faulty ignition coil | Test coil and replace as necessary | |
| Improperly seated valve(s) | Test cylinder compression, repair as necessary | |
| Faulty valve spring(s) | Inspect and test valve spring tension, replace as necessary | |
| Incorrect valve timing | Check valve timing and repair as necessary | |
| Intake manifold restricted | Remove restriction or replace manifold | |
| Worn distributor shaft | Replace shaft (Distributor systems only) | |
| Misfire at all speeds | Faulty spark plug(s) | Clean or replace spark plug(s) |
| Faulty spark plug wire(s) | Replace as necessary | |
| Faulty distributor cap or rotor | Replace cap or rotor (Distributor systems only) | |
| Faulty ignition coil | Test coil and replace as necessary | |
| Primary ignition circuit shorted or open intermittently | Troubleshoot primary circuit and repair as necessary | |
| Improperly seated valve(s) | Test cylinder compression, repair as necessary | |
| Faulty hydraulic tappet(s) | Clean or replace tappet(s) | |
| Faulty valve spring(s) | Inspect and test valve spring tension, repair as necessary | |
| Worn camshaft lobes | Replace camshaft | |
| Air leak into manifold | Check manifold vacuum and repair as necessary | |
| Fuel pump volume or pressure low | Replace fuel pump | |
| Blown cylinder head gasket | Replace gasket | |
| Intake or exhaust manifold passage(s) restricted | Pass chain through passage(s) and repair as necessary | |
| Power not up to normal | Incorrect ignition timing | Adjust timing |
| Faulty distributor rotor | Replace rotor (Distributor systems only) | Incorrect spark plug gap | Adjust gap |
| Faulty fuel pump | Replace fuel pump | |
| Incorrect valve timing | Check valve timing and repair as necessary | |
| Faulty ignition coil | Test coil and replace as necessary | |
| Faulty ignition wires | Test wires and replace as necessary | |
| Improperly seated valves | Test cylinder compression and repair as necessary | |
| Blown cylinder head gasket | Replace gasket | |
| Leaking piston rings | Test compression and repair as necessary | |