4.3L engine, CMSFI. Code P0300 - Mulitple/Random misfire. Barely idles, runs very rough, smooths out at higher rpm but still is missing. After clearing codes, will repeat consistantly. Have replaced ignition coil, cap, rotor, plugs, plug wires, fuel pressure regulator, fuel filter. Little or no improvement. Checked fuel pressure at shrader valve - will fluctuate wildly between 55 to 60 psi at idle, smooths out to 52 psi at or above 2,000 psi. When replacing the fuel pressure regulator, I noticed that there was a port on the regulator as if there should be a vacuum hose, but none was present. Should there be one? Any ideas? I have a lift and lots of tools, and would consider myself to be an above average mechanic, but this one has me stumped. My daughter has a 1995 Blazer, but it is a CMFI injection, a little different. I have never worked on the CMSFI before.
have the same problem?
Friday, February 27th, 2009 AT 7:24 AM