I would swap the coils, and not the plugs when diagnosing misfires. NGK and Champion spark plugs are recommended for our Chrysler/Fiat vehicles (Platinum plugs for vehicles requiring replacement every 100k, and Copper plugs for vehicles requiring replacement every 30k). Autolite spark plugs seem to fail quickly in Chrysler engines.Getting a crazy popping sound from under the car still. Sounds like mini detonations. I suspect the cats are totally wrecked. They look bad from the outside and the popping sounds like in that area. Also the previous owner was driving with misfire code and bad plugs for possibly 9+ months. Not getting a cat code only random misfire.
These accumulated deposits can result in spark plug fouling leading to spark plug misfire due to insufficient voltage for spark to occur. If the spark plug tip temperature is higher than 850°C the spark plug will overheat which may cause the ceramic around the center electrode to blister or crack and the electrodes to melt.
MEMBER. 1996 DODGE CARAVAN. I have a 1996 Dodge Grand Caravan with the 3.8L engine. In January, the car started to shudder and engine misfired. The ODB II scan read P0305-Cylinder no. 5-Misfire Detected. I replaced all six spark plugs and wires with Bosch Platinum Plugs and Bosch wire set. The car ran fine for two months.The spark plug in cylinder 1 turned out to be carbon fouled, another had some deposits. Replaced all 6 plugs and it ran better for a few days then the misfire came back and started running rough again. Plug 1 fouled again. I replaced it, swapped wires, checked it a day later.. fouled again. Also, the plugs in cylinder 2 and 3 are starting to foul.