try replacing the "Knock Sensor" that is located under the intake manifold. It costs about from $20-40 and is easy to replace. You may though have to remove the manifold. First try to get at it by taking the rotor and cap off. If that won't get yoiu in enough, try unbolting the power steering reservoir and then try. It is located on the block...not in the cylinder head! The one in the head is the temp sending unit.

pull the vacuum line of the ignition brain and see if there's vacuum. the lines break or the hoses fall off. if there's vacuum, put it back and put a timing light on the car. run the throttle up and see if the timing advances. no? needs a brain. if it advances, then check the base timing. 12 degrees btdc. chrysler ignition will rattle on sudden acceleration, for a second or 2, this is normal. sustained ping could low octane-the 84 b23 automatics are 10.3 compression, didja know that? the knock sensor could be dead, or the harness to it is broken, both possible. also, carbon on the tops of pistons and the bottoms of valves will raise compression, although it rarely comes on suddenly. good luck, chuck.

hi there try running higher octane . if it goes away then your timing may be off. too far advanced. but i dont know how it changed all of a sudden. unless the distributer is loose.