Whenever the air-fuel mixture in your car combusts somewhere beyond the engine's cylinders, an engine backfire occurs. If left unchecked, a car backfire can cause harm to the exhaust or intake of your car — and it also means that the engine of your car does not generate as much power as it should, and is wasting a lot of fuel. Therefore, a car that backfires repeatedly is desperately in need of repair.
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Car Backfire on Purpose
Although a car backfire is typically something you'll want to prevent, there are instances when it is done on purpose for the fact that it exhibits an impressive impact. You'll be able to get your car to look like a drag racing monster with your car roaring, along with flames and smoke strutting out its back. In modern automobiles, a little backfiring on deceleration occurs by design, for added sporting sound. For older cars it can still be possible by doing something to create it on purpose. Bear in mind, however, that it can be really dangerous to backfire a vehicle, so it's normally inadvisable unless you know the pros and cons, and the safety measures of what you will be doing.
Backfiring for Older Cars
Take into account the reasons why cars backfire. Although backfiring in old cars can be done manually with relative ease, it is crucial that one understands what backfiring is, and what causes it. Like the fact that it is a misplaced spark or sudden blast of fuel or air that causes the engine to burst loudly.
Some modern vehicles are made with systems through an Engine Control Unit (ECU) to regulate these aspects, while older cars before 1990 are much more malleable. It is important to bear in mind the reasons why regulating systems were integrated in the vehicle in the first place. Excessive backfiring can be detrimental for your vehicle, and can result in having to replace parts in the long run.
Now for the actual method begin by starting your vehicle bringing it to a steady revolution. Prep the car as you normally would with safety checks. Check for dripping oil most especially as you're about to be charging an open fire.
Double check the location. It certainly must be open and cleared of things that might catch fire. This includes any audience. A distance of around 10 meters or 33 ft should be good. After the safety check, prepare your car for some backfiring by turning the engine off again, with your foot resting on the gas pedal. Do not start to move fast while turning on the engine, keeping the pressure light.
After waiting for a few seconds, restart the car. When it starts up, keep your foot on the gas pedal. Press the accelerator down as hard as you can once it's up. This will trigger the vehicle to backfire.
Backfiring for Modern Cars
Be mindful that your car might have backfired already. When it comes time to decelerate, some modern sports cars actually backfire purposely. Mostly, this is done to add to the appearance and bravado of the vehicle. Given that a more recent model is far more difficult to backfire properly, you may want to take advantage of the existing opportunities. After reaching a respectable (~60 mph) pace, try decelerating, and see if you can hear it. Better still, get a buddy to look at the exhaust while you drive and slow down.
Prepare the car accordingly. Before they can backfire safely, modern cars (roughly after 1990) need more tuning. The chassis of the car is not usually built to withstand it, since the ECU is there as a failsafe against backfiring. A more robust exhaust port will mitigate the car's body damage.
Put in a new ECU input ECU. There should be a port with a Flash Tune Kit depending on the car model that is hooked up to your car, where you would be able to change the software of the ECU directly. This is to alter the times and rates at which fuel is injected. Sadly, hardware and software ECU modding can be pricey, and could cost you over $1000 dollars. It is important to note that ECU mods are often specific to certain models, so research needs to be done to find the suitable one that would suit your vehicle.
Control and customize the injection levels in the ECU.This is where it becomes complicated, since it demands that you have an existing understanding of the specifications of your car. You have to decide on what engine RPM you want set before your vehicle starts backfiring. Choose an RPM to cut all fuel if you only want the roar and pop of a backfire. But if you want to see flames, you have to set it in a higher number for a given RPM.
It goes with the territory that it is more risky to add extra fuel. If you're a newbie to this undertaking it's recommended that you stay on the safer side. Although the requirements will differ depending on the model of the car and the type of ECU pack, you will want to access the input and cut fuel intake at the RPM at which you want your car to pop at
Place the given RPM intake at the most negative integer the program can allow when it's a Flash Tune Kit you're using. To cover the range of a few hundred RPMs, input these negative integers. It will do the ‘trick' for your engine to start popping.
Wrongly entering a number could mistakenly ruin your vehicle. It is not recommended that you even contemplate doing this without any motor work experience.
Car Backfire Causes
What if a car backfire is not stimulated on purpose. This could be a symptom of a number of issues to look into. Here are the common causes for a car to backfire:
Issues on the Ignition System
Backfires and other engine output issues can be triggered by any issue that upsets an ignition system spark. For the spark to leap the gap between the middle and side electrode at the tip of a spark plug, an engine requires a couple of thousand volts of potential. The lack of proper maintenance of the ignition system can trigger problems that eventually lead to backfires.
A spark plug gap, for example, will widen after the plug has been in operation for months and make it hard for the spark to leap. Also, the electrodes may be separated by carbon build-up, preventing proper combustion. Unburned fuel reaches the exhaust system where it can backfire.
A worn out or damaged spark plug wire may trigger the same type of problem. A bad wire can make it impossible for the spark to move, weaken the spark, or simply force it to the ground or into an adjacent wire, resulting in a backfire. A defective ignition coil, distributor or rotor may produce the same result and cause a more repeated backfire.
Issues on the Engine Sensor
A bad mass air flow (MAF) sensor and other sensors are used by an engine computer to calculate the amount of fuel to inject into the engine in accordance with operating conditions. So if a sensor is not able to send the correct signal, the system may deliver too little fuel leading to a lean fuel condition. A bad MAF sensor also usually causes the Check Engine Light. Many other emission related sensors the computer depends on can fail too, causing the CEL to come on.
Regardless of a computer pointing to a possible bad sensor, still make sure to test the sensor before replacement because many times issues on different components or parts can make the sensor look seemingly bad.
Exhaust Gas Recirculation System Issues
A car backfire is one of the problems that could arise from exhaust gas recirculation (EGR) system issues. Its valve can cause all kinds of problems when not functioning as it should. The EGR technology is made for the reintroduction of a measured quantity of exhaust gases back into the reburner cylinders. This lowers the temperature of combustion and harmful pollutants such as NOx (nitrogen oxides).
If the engine speed rises and closes while the engine is idle, the EGR valve opens. A stuck-close valve, however, will not allow exhaust gases to recirculate back into the chamber of combustion. This occurs often when carbon deposition blocks valve passages, the valve (on vacuum controlled valves) is not operated by a vacuum leak, an electronic control sensor fails or the valve itself is damaged. Inspect for vacuum leaks, including intake and exhaust gasket leaks and leaks on vacuum hoses, and air intake boot. During engine operation, this condition will raise the cylinder temperature, allowing a flame to spread quickly through an open intake valve and burn the fuel coming in, resulting in a backfire.
The fault is identical to the one shown by a defective accelerator pump carburetor. So if you have failed to inspect the EGR valve for the last 2 to 3 years, do it as soon as possible and see to it that the valve still opens and no passages are blocked. Double check for carbon buildup along the passages of the valve and the intake manifold where the valve is mounted. Note that in some cases, depending on the car model, removal of the EGR valve to be inspected can be difficult, but in the majority of cases you will be able to do it at home.
Issues on the Injection System
Backfiring problems can also begin in the fuel system. Usually, the combustion mechanism weakens when an injector clogs or wears out, allowing the air-fuel mixture to lean, and the fuel fails to burn properly. And when excessive unburned fuel reaches the exhaust system, the fuel ignites with a loud bang. You must check the fuel injectors that it's properly operating by using a mechanic's stethoscope and digital multimeter.
Bad Engine Timing
An engine backfires when the combustion takes place outside the engine's combustion cylinders. Within every cylinder, fuel and air are mixed in a precise ratio at the precise right time. The entire mixture ignites with a spark, and that results in explosions that power your car. But when the timing of the spark is a bit off in the engine cycle it causes unburnt fuel and air to flow through the exhaust and that super hot fuel reaches the tailpipe and mingles with the highly-flammable oxygen from the outside air. This unspent fuel is combusted in the exhaust, rather than in the engine resulting in a loud bang and even causes visible flames coming out of the exhaust tip.
In modern engines the timings are controlled by computer so most engines are guaranteed to burn up 100% of the fuel in every combustion chamber each time. So a car backfire is more common to older, carbureted engines with distributor caps.
Leaks on the Exhaust System
Car backfires can also come from the exhaust as a result of air leaks in the system. As the content of oxygen rises, it causes loud combustion of partly burned or unburned fuel entering the system. A crack in the exhaust manifold gasket, an exhaust pipe sealing ring, or a damaged pipe can allow the extra oxygen to come through.
In addition, some car models are configured with an air injection system. iIf the system injects air when it shouldn't or fails to work it results in unburned or partially burned fuel in the exhaust gases to backfire. So it is important to inspect the system if it is properly operating, most especially the check valve. Refer to the repair manual of your car.
Conclusion
Paying attention to proper regular maintenance in key systems of your car like fuel, ignition and emissions is a must in keeping your car running in top shape. Backfires whether on purpose or not is never healthy for your car so always be on top of everything.