any idea what would cause this...the engine, at random times, will not go above 4000 rpm's. the check engine light also comes on when this happens. at 4000 rpm's it acts as if it would if it was redlining. any thought would be greatly appreciated. oh, its an 04 civic 1.7L. thank you

 

If possible, drive your Civic to AutoZone where they will retrieve the trouble code free of charge.

 

Kind of sounds like it is in 'limp mode'
Have you done anything recently (modifications) to your car?

 

no i havent.

 

get the codes read at an autoparts store for free.