Misfire and drivability complaints tied to misfire codes are common in your shop. So how do you deal with them effectively? One critical question often gets skipped: How long has the misfire been going on? That’s a key diagnostic detail. The longer the issue persists, the greater the risk of misfire catalytic converter damage.
What Happens During a Misfire
Here’s what happens in a misfire: fuel and air enter the cylinder, but no combustion occurs. This can be due to a bad spark plug, ignition timing issues, or related causes.
That unburned air-fuel mix then exits the cylinder and enters the catalytic converter. Once there, it can ignite and create excessive heat. That heat may damage the ceramic substrate inside the converter.
Why Duration Matters in Converter Inspection
Understanding how long the misfire has been active helps you assess whether the converter has already sustained damage. If it’s been more than a week, odds are good the converter has suffered damage from unburned fuel.
This is where you need to expand your diagnostic process. Look beyond the cylinder. If you see a P0420 code, reduced converter efficiency, or high backpressure, don’t ignore it. You may be dealing with a clogged or overheated converter.
Don’t Stop at the Misfire Code When Diagnosing Misfire Catalytic Converter Damage
When diagnosing a misfire, check downstream effects. If the spark isn’t firing, fuel and air pass through unburned and ignite inside the converter. That raises temperatures dramatically and can cause misfire catalytic converter damage.
So remember: always ask how long the misfire has been occurring, and inspect the converter accordingly. The converter might be suffering, even if the misfire seems minor at first glance.
This video is sponsored by Auto Value and Bumper to Bumper.
