Misfire and drivability complaints with misfire codes is very common at your shop. What often gets left out is asking that customer, “how long has that misfire been going on?” The longer a misfire is around on an engine, the chances of damaging the catalytic converter are a lot greater.
Just think about a misfire. You have fuel and air going into the cylinder, and it is not ignited because either the spark plug is not working or the timing is off. Then that air and fuel gets put into the catalytic converter. When it’s there, it ignites and creates heat and possibly damages the ceramic substrate inside the catalytic converter.
This is why it’s critical to understand how long the issue has been occurring and extending your diagnostic process to a catalytic converter. In some cases, this is going to be clogged. In some cases, the efficiency numbers are not going to be there, and you may have a P4020 code.
When this happens, you’ve got to do further diagnosis on the vehicle. But going back to that question —if they say it’s been going on for more than a week, chances are the converter could be damaged due to the severity of the misfire probably from that vehicle.
So just keep these two things in mind. If you have a misfire code, make sure you’re checking downstream, because if that spark plug is not firing the air and fuel, it’s going into the cat getting burned and causing higher temperatures.
This video is sponsored by Auto Value and Bumper to Bumper.
Watch more episodes of Tech IQ here.
