What would cause a trouble code PO 300 on a 1998 Chevy Blazer. The truck will run good sometimes. When it runs bad it will stumble at low speed acceleration. It will run fine wide open. Dealer looked at it and thought it was egr vale. I replaced it and it runs a little better but still stumbles.

Trouble code PO300

Cougar January 24, 2011, 9:38am 2

My first thought is try replacing the plug wires if they haven’t been replaced in a long time.