Please refer to CarGurus Terms of Use. Content will be removed if CarGurus becomes aware that it violates our policies. How much does a resonator effect backfire loudness?? Report Follow. Mark helpful. Your Answer:. Upload Photo Photo optional. Related Questions. Start a new Subaru WRX question. Own this car? Leaks in the exhaust system, sometimes called vacuum leaks, can sound more like a screech than a bang as excess air gets sucked in.
All this extra air mixes with the fuel, creating an incorrect ratio for proper combustion. Even something as simple as a dirty air filter can potentially trigger a backfire. Since air filters allow clean air to flow into your engine, a dirty filter can inhibit the flow of air into the intake, creating a poor fuel-air ratio.
Injectors that supply too little or too much fuel to the cylinder can also create a poor fuel-air ratio. Spark plugs that fire out of turn or not at all can also cause backfiring. Shorts in wiring, incorrect wiring, or damaged distributor caps that deliver the charge to the wrong plug at the wrong time are much more common in older vehicles. But even in newer cars and trucks, plugs can malfunction due to carbon buildup or wear out over time.
In the four-steps of engine combustion, timing is everything. If the timing is off, valves might open or close at the wrong time, and the spark might arrive early or late. Any time the fuel-air explosion is not properly compressed, ignited, and contained, a backfire can occur. Newer engines with computer-controlled timing are more reliable, and backfires are less likely.
Not all backfires occur when you start the engine. Sometimes one can happen when you shift gears. However, that loud pop that you hear when shifting is, in fact, an afterfire. Most of these occur on manual vehicles where a clutch is used to shift gears. As you press in your clutch and go from one gear to the next, fuel can continue to enter the cylinders, especially if you switch gears at higher RPMs. All this unburnt fuel builds up in the exhaust and ignites when you release the clutch.
Though this might sound alarming when it happens, an afterfire when shifting isn't necessarily damaging your vehicle. Does the sound your car makes upon starting remind you of Fourth of July fireworks? Then it's time to take care of those combustion problems! Your WRX uses a series of sensors to measure the air and fuel going into the engine, as well as the oxygen content of the exhaust. A rich condition can occur when one of these sensors has failed. Ignition timing is a very common cause of backfiring.
Many modern vehicles use variable valve timing VVT. Your WRX uses a timing chain or belt to keep the camshaft s and the crankshaft synced together. If it jumps a tooth, it can throw the entire vehicles timing off to the point that it can backfire. The best way to start is to start with the check engine light.
If it is on, you can pull the diagnostic trouble does with a good code scanner. It would be best to start with what is easiest. Taking a look at the spark plugs and determining their health is the easiest thing that you can do. It is also one of the most common reasons that a gas engine backfires.
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