Starts and idles fine when you reve the engine it makes a popping back fire from tail pipe
My car has an automatic transmission.
The backfire can be can be caused by a few possibilities. From what you’ve described, about the popping out of the tailpipe, you either have excessive amounts of air getting into the exhaust, a bad exhaust valve, or a spring that cannot close the valve fast enough when you rev up the engine. I suggest having a certified mechanic, like one from YourMechanic, diagnose the noise and try to isolate to one cylinder. Then remove that valve cover and check the exhaust valve spring to see if it is broken.
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