Symptoms of an Incorrect Firing Order
What an engine does when the firing order is wrong, and why extended cranking or driving on a known misfire causes further damage.
A wrong firing order rarely produces a subtle symptom. It usually announces itself immediately after ignition work.
What you will see
Do not continue extended cranking or driving with a known misfire. Unburned fuel can damage a catalytic converter, wash oil from cylinder walls, or ignite in the exhaust. Recheck identification, No. 1 compression TDC, bank numbering, and every connection.
- Cranks normally but will not start after plug-wire or engine work.
- Popping through the intake, carburetor, or exhaust during cranking.
- Severe shaking, dead cylinders, low manifold vacuum, or raw-fuel odor.
- Multiple misfire codes that appeared immediately after connectors were disturbed.
- Timing-light marks that are unstable or cannot be brought into the expected range.
- Exhaust manifolds that warm unevenly because one or more cylinders are not contributing.
Values, sequences and intervals are vehicle-specific. Use the specification page for your exact year, engine and component alongside this procedure, and follow the manufacturer document it cites.
Symptoms of an Incorrect Firing Order FAQs
Can I drive a short distance with a bad misfire?+
Avoid it. Unburned fuel can destroy a catalytic converter, wash oil from the cylinder walls, or ignite in the exhaust system.
Why does the engine backfire after replacing wires?+
The usual causes are crossed wires, No. 1 indexed on exhaust rather than compression TDC, wrong bank numbering, or the wrong order for the installed engine/camshaft.