My wife’s 2005 PT Cruiser has been running rough for the past year. One mechanic ran a scope test and found no electrical issues. Another said it was the air conditioner loading the engine. He completely flushed, cleaned and recharged the AC system. While the AC works better than before, it still vibrates badly when idling. This happens even when AC is turned off. It seems worst when in reverse.
I found your post while searching for a similar problem. If you haven’t found a solution to your problem here is something that might help you:
There is a service bulleting from Chrysler that describes your problem pretty well.
GROUP: Vehicle Performance
DATE: June 1, 2004
Flash: Idle fluctuation and or MIL Illumination Diagnostic Trouble Codes P0300, P0301,
P0302, P0303 or P0304
This bulletin applies to PT Cruisers 2004/2005 built on or before May 24, 2004.You can check the build date on the driver door on the side.
This bulletin involves replacing the affected spark plug, ignition wire and/or reprogramming
the Powertrain Control Module with new software.
My local library has access to the Chilton database and maybe yours has access too? You can try that and see if you can find the bulletin and then take it to your mechanic or maybe dealer because they are the only ones that do the programming.
Hope this helps you.
Thanks for this info. I would have thought that a defective spark plug or ignition wire would have shown up on the scope analysis. On the other hand a SW update may be required. A trip to a dealer may be a good idea.