2003 OLDS ALERO,PROBLEMS :HAVING TROUBLE GETTING IT TO START ,REPLACE BATTERY & STILL
HAVING PROBLEM.WHEN ENGINE IS RUNNING IT IDLES VERY ROUGH
If you can scan the computer system for any trouble codes. Repair any that may come up. If there are no trouble codes then continue trouble shooting.
Inspect all vacuum hoses from the engine. A cracked or corroded hose can cause a poor running condition.
Check to see if there are any fouled spark plugs (dead cylinder) this can cause a rough idle.
Check all spark plug wires for poor resistance or corroded ends. One bad wire can knock out two cylinders. A bad coil will also knock out two cylinders.
Check the fuel pressure. The fuel pressure should be between 50 and 60 PSI. There was a service bulletin on a fuel pressure problem involving the fuel strainer in the fuel tank. Its number is 05-06-04-026A dated 4-27-2005. It describes fuel pressure loss caused by a clogged screen in the tank.
Try these few suggestions and get back to me when you can with the results.