First things first: backfiring is harmful to your engine. It’s a sign that something is not working right. That out of the way, let’s define the issue:
Backfiring is when fuel combustion occurs outside of a combustion chamber.
Fuel is somehow getting out of the combustion chamber and because the engine is hot, it combusts. This is not good.
That said, it’s not the end of the world. The first thing you need to do is figure out where the backfiring is happening, which you can do by listening. Is it coming out of the muffler? Terrific! Now you know! Is it coming from the engine itself? It’s probably happening somewhere in the manifold. Either way, you learn something by the location.
If your car is old, the carburetor manages the mixture of air and fuel, which is a common culprit for backfiring. If your car is newer, it has a computer called the engine control unit that manages everything. The ECU could therefore be the problem, or the mass airflow sensor.
There are lots and lots of reasons why your car is backfiring. Rather than embark upon an expensive fact-finding mission with your technician, we recommend taking care of some basic maintenance that, a) you already need, and b) could very well be the source of your backfiring.
Old spark plugs and wires, clogged fuel filters, worn fuel pumps, erratic engine timing, and air flow issues are related to that delicate balance of fuel and air that is the key to healthy combustion.
An imbalance in one area can cause the other areas to work harder to compensate. That creates the potential for faster wear of the system as a whole, and for anomalies that shouldn’t cause backfiring, but do. Therefore, your best bet for keeping combustion where it belongs is to ensure the health of your combustion process. It’s better to fix the 98% that’s easy first rather than going after the rogue 2%.
Now that you know a little about backfiring it shouldn’t seem as intimidating a problem. Rather than shy away from a potential dream car with a slight hiccup, you now have the knowledge to address the issue, which gives you more confidence for keeping your classic car in your garage.