Q: why is engine back firing

asked by on December 18, 2016

I just rebuilt my 5.2 L 1998 dodge because I was burning oil first start after rebuild truck idles good not rough but pops back though exhaust almost in rhythm with the revolution of the crank also when accelerating the rpm climbs rather than jump seems to have poor response why ?

My car has 120000 miles.
My car has an automatic transmission.

Backfiring through the exhaust generates sudden high-pressure events in the exhaust system that can do serious damage if left unchecked. Request a backfiring inspection by a professional mechanic as soon as possible.

Among the causes of backfiring is the engine is being supplied with more fuel than it needs to burn efficiently. Too much fuel has many causes including leaking fuel injectors and a dirty air filter. With too much fuel to create an explosive, fast-burning flame, the fuel burns slower, and the burn doesn’t complete before the exhaust part of the engine cycle. When the exhaust valve opens on that cylinder, the extra air allows the unburned fuel to explosively burn and the popping noise of a backfire is heard. Another causes of backfiring is delayed ignition timing. This is also known as retarded timing. If the ignition cycle begins too late in the combustion chamber, fuel can ignite as the exhaust valve is opening. Ignition system faults such as a cracked distributor cap and carbon tracking on spark plug wires can cause the spark to cross over from one spark plug wire to another in close proximity. When that happens frequently a carbon track forms, which is like a shortcut for the spark. It causes a misfire very similar to that of a cracked distributor cap. Carbon tracking can also form on spark plug wires or ignition coils that are mounted directly onto the spark plug. In the same way, part of the spark takes an incorrect path, and the remaining spark isn’t enough to ignite the fuel, leaving some in the cylinder. The next ignition may be enough to fire the spark plug, this time with extra fuel in the cylinder. The flame doesn’t burn as explosively and isn’t complete before the exhaust valve opens. The rapid burn that occurs while the exhaust valve is open causes a backfire.

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