I have a 2003 GMC Sierra 5.3L with 126,000 miles. My problem began with sluggish performance, check engine light flashing when under a load and it was hard to start. I pulled the codes and found the P0300 Random Misfire code. I replaced the plugs/wires, fuel filter, air filter with no joy.
I checked the fuel pressure regulator and found fuel in the vacuum line. I replaced the regulator and the code dissapeared as did the starting problem. However; the engine still bogs down and will knock a little when under a load such as going up a steep hill, when I hit the passing gear, etc. I took it down the highway this morning and it struggled to get above 70mph.
have the same problem?
Sunday, June 12th, 2011 AT 4:53 PM