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92 Cadillac Deville exploding muffler

92 Cadillac will start and idle fine but intermittent missing and popping of exhaust before and after warm up. When the loss of power and backfiring get extreme, I will pull over, cut engine, and wait a few seconds. This will clear the problem for an hour or a day. If I do not pull over in time the exhaust explodes(twice with in a week). A tune up was done last month, with a check of the timing, O2 sensor, and wiring harnesses. What would be the causes and solution for repair? I do enjoy the look of the tailgater when the muffler goes.

Does the exhaust smell like gasoline?

You have significant burnable exhaust collecting in the exhaust manifold(s), the catalytic converter, and the muffler until an ignition source, probably a firing cylinder, sets the collected mixture off. Most likely it is an intermittant loss of ignition. So it could be the coil, the igniter, the distributor pickup coil, or the signel from the Electronic Control Module.

Since this is intermittant, you may need to use the parts replacement method of trouble shooting. I would definitely do a wiggle test on all the ignition wiring.

Good luck on this.

No gas smell from muffler.

1992, this must still be the old 4.5 liter aluminum pushrod engine which uses a version of the old HEI system…Most modern mechanics are baffled by this old technology…

No this is the 4.9 liter

The 4.9 and the 4.5 are virtually the same design. They were replaced by the Northstar 32 valve OHC engine in 1993…Carefully examine the distributor cap, rotor and coil for cracks or other problems…The ignition module, located inside the distributor, has been known to break the fine wires that connect it…Gently tug on the wires where they enter the module and see if they stretch easily…

You could be having total computer failure, like the 80’s GM cars could have. Price an engine computer and go from there. If it is $200 or less, change it. If it’s more than that; it’s fourth down, kick or keep.