Rough Running
 

my 2007 hhr stopped running.
replaced battery.
replaced alternator.
now it runs rough.
check engine light is on and it displays (ENGINE SPEED REDUCED)

can anyone tell me whats wrong????

Take it to your local auto parts store, Napa/Autozone/Advance/etc, and have the codes pulled. Once you get them, post them here and we'll have a better idea of what direction you should look in to fix the issue.

X2 - without downloading the code from the engine check light, anything we can suggest would be a total guess. If the car is not drivable to the autoparts store, borrow a OBDII code reader (it must be CAN-compatible in order to get the codes to download).

Maybe somebody should make an auto reply for "why is my CEL lit up?".:corny::propeller:

Maybe a "Sticky" called "Check Engine light on, here's what to do", then give the steps needed in order to get the codes pulled for further diagnosis.

Spark plugs maybe or plug wire - boots

ahhh, there are no spark plug wires............