Well after my car starting stumbling one day (anytime throttle was pressed down more than 1/8th of the way) i replaced the PCV valve, fuel filter, spark plugs are only a year old, and replaced 2 ignition coils. Now the car doesnt stumble as much, but at about 3000RPM when accelerating maybe 1/3-1/2 throttle, it starts to surge sorta. But its not nearly as bad as the missing i had at idle (sometimes) and when accelerating anymore than 1/8th. Im completely stumped, and any help would do. Sorry for the long post.

Cheers.
Josh

 

MAF sensor might be shot.

 

check your wiring harness.....my car was doing that for 2 years and i spent 600 bucks in replacing stuff to find it out was a broken maf ground wire in the harness coming from the firewall.....if you move the harness around with the engine running and the car stumbles then you know its the harness

 

check the plugs again