Delayed timing means that the ignition cycle of your engine starts late in the combustion chamber, and ignites the fuel as soon as the exhaust valve is opening instead of waiting for it to be fully open. If the cap is cracked, it allows moisture to creep in, which causes the electrical spark to jump to the wrong cylinder, causing a backfire.
Carbon tracking can come into play in a variety of situations, the first situation involving sparks that are generated by wires on a distributor cap, can start to hop from one wire to another very quickly and thus a carbon track is formed which is essentially a shortcut for the spark. For instance; if you accidentally plugged one of the sparkplug wires onto the wrong spark plug, it is going to cause spark to ignite that plug at the wrong time which could cause an exhaust backfire, or an intake backfire, depending on where either valve is at the time the spark occurs.
If it sparks when the intake valve is open, you're going to get a pop back up through the carb. If it sparks when the exhaust valve is open, then it'll cause a bang out the exhaust. Basically, when that plug sparks out of turn, it lights the fuel in the cylinder - and that pressure has to go somewhere This usually goes away once the engine warms-up.
A cold engine needs more fuel to run, and a warmer engine runs more efficiently and needs less fuel, so if you are only spitting when the engine is cold, then most likely it's due to a lean condition. You could also check to make sure your choke is working. If this is the case, your Check Engine light might be screaming at you. 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.
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