Check your spark plugs to make sure they are clean and properly gapped. Either one can cause misfires, improper timing is also possible. The injector may also be clogged which may result in failure to dispense the correct volume of fuel.
There are a variety of things that can cause a miss while in idle. A worn out spark pug can cause a miss. Worn out ignition wires can also cause a misfire. A worn out distributor can also be the cause and lets not forget the possibility of timing belt/chain damage or a dirty fuel system.
It could be several things. One your spark plug may be bad. Two the spark plug boot or lead wire may have a short in it. Your ignition module may have damage. These vehicles are electronic ignition so often the problem will be in a short or bad plug, which can be fixed.
There could be something wrong with the transmission on your PT Cruiser. I would have that checked out by your local mechanic then you may have to purchase a transmission that could cost up to around 3000 dollars.
It is more than likely related to some problem in the ignition or timing system. Check to make sure all you plugs and wires and in good shape. Also check that your coils are in ok and that none of the connections are loose.
The likely causes are a vacuum leak, a bad injector, a bad oxygen sensor trying to constantly compensate for some other problem, or you filled the car with some bad gasoline. Try gas treatment and injector cleaner first.
