I would start to suspect the Mass Air Flow sensor at this point.
A few notes to point out.
Revving the engine in Park will usually result in not going over the programmed rpm limit in the PCM. This is to protect the engine from excessive "free revving" - that is revving the engine without a load.
Also to check is fuel pressure while driving at the affected speeds. A loss of fuel pressure or restricted injectors can also cause a miss. Injector O-rings are another possible cause of trouble. They do get old and crack - allowing unmetered air to enter the intake stream and lean out one or more cylinders.
But. My gut feeling is that the MAF is out of calibration or that there is an air leak in the intake path.
Tuesday, May 12th, 2009 AT 12:24 PM