Engine Performance problem
2000 Chevy Malibu 6 cyl Front Wheel Drive Automatic 88000 miles
----------------------------------------------------------------
I have a code of p0300, I already change the Spark Plugs and wires and still does the same thing. When i rev the engine it seems good but very rough at idle.

3.4 motor?

The multiple misfire code on this engine makes me think of an intake manifold gasket leak. Are you losing any coolant?

The 3.8 motor has some issues with the intake itself, again a coolant loss is associated with this.

Service Writer wrote:

3.4 motor? No, I am not losing any coolant. The engine is a 3.1 and it was just rebuit by someone. The multiple misfire code on this engine makes me think of an intake manifold gasket leak. Are you losing any coolant? The 3.8 motor has some issues with the intake itself, again a coolant loss is associated with this.

I would think that "someone" would warranty the work if it comes down to a mechanical issue.

I was thinking Impala when I posted this. The 3.1 is an intake problem too: www.Dexcoolsettlements.com

Assuming there are no vacuum leaks, I would next check the fuel pressure for the right spec.