Symptoms
- Loud bang or pop from the exhaust, sometimes with a visible flash at night
- May happen on deceleration, acceleration, or gear changes
- Possible rough running alongside it
- Check engine light sometimes present
Likely causes
- CommonIgnition misfire sending unburned fuel to the exhaustFuel that doesn't burn in the cylinder can ignite later in the hot exhaust.
- CommonExhaust leak near the manifoldA leak lets extra oxygen mix with exhaust gases, causing pops as unburned fuel ignites.
- PossibleWorn spark plugs or ignition coilInconsistent spark timing can send unburned fuel downstream.
- PossibleLean fuel mixtureToo little fuel can cause incomplete, delayed combustion that pops in the exhaust.
- Less commonAftermarket tune or modified exhaustNon-stock tuning or exhaust setups sometimes intentionally or unintentionally cause pops on deceleration.
What to do
- Get the check engine light scanned for misfire or fuel trim codes.
- Check for exhaust leaks near the manifold, since these commonly cause popping.
- Inspect spark plugs and ignition coils for wear or damage.
- Note exactly when it happens (accelerating, decelerating, shifting) and mention this to a shop.
- Have fuel trims checked to rule out a lean condition.
- Address the underlying misfire or leak rather than just tolerating repeated backfiring, since it can damage the exhaust or catalytic converter over time.
Tools and parts
- OBD-II code reader
Spark plugsSearch: “spark plugs for [year make model]”
Exhaust gasketSearch: “exhaust manifold gasket for [year make model]”
When to call a pro
See a shop if backfiring is frequent or loud, since repeated unburned fuel igniting in the exhaust can damage the muffler, catalytic converter, or other components.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.