This is the third time now I've had this problem in six months. 1st time it went away by itself. 2nd time I used injector cleaner and a full tank of 93 octane. It ran fine but still had a SES light I took it to Autozone who scanned it and read #4 cylinder misfire. Now it's back just like Arnold. I suspected the injector. Well I pulled off the #4 cyl wire and pulled out the plug. They both looked ok so I put them back in. Engine now runs fine. I guess the wire wasn't on all the way. The car has 24k miles on it but now I know you can never be certain of anything untill you actually check it.