I have a 2003 Honda Civic Ex and it wont go over 20 and will stall when you rev it to high RPMs. I have heard many different things that it could be but thought this would be the best place to ask. Any suggestions are appreciated. Thanks!

 

You're most likely in limp mode so you don't kill the engine with mis-fires. Pull the codes and post back. Also try to reset the ECM/PCM (With the ignition OFF pull the #6 fuse in the under-hood fusebox for at least 10 seconds) and see how quickly it goes into limp mode again.