[acutron42]

Here is some info from Alldata. There are 44 results on this issue & too much to post. It could be a faulty crank position sensor but without seeing comprehensive scan data I would start with the basics. The maf sensor & fuel quality are low on the list in other sections but rule these out first as they are worth exploring for ease & cost.

DTC P0300

The ECM detects a crankshaft rotation speed variation indicating a misfire rate sufficient to cause emissions levels to exceed mandated standards.

DTC P0301, P0302, P0303, P0304, P0305, P0306, P0307, or P0308

The ECM detects a crankshaft rotation speed variation indicating a single cylinder misfire rate sufficient to cause emissions levels to exceed mandated standards.

Action Taken When the DTC Sets

* DTCs P0300-P0308 are Type B DTCs.

* When the MIL is flashing the fuel injector may be disabled for the misfiring cylinder to protect the catalytic converter.

* Depending on the conditions that set the DTC, the engine may go into Open Loop.

Conditions for Clearing the MIL/DTC

* DTCs P0300-P0308 are Type B DTCs.

* The DTC must run and pass under the same operating conditions that were present when the DTC failed.

Diagnostic Aids

* The Crankshaft Position System Variation Learn procedure may need to be performed. Refer to Crankshaft Position System Variation Learn See: Crankshaft Position Sensor > Programming and Relearning > Crankshaft Position System Variation Learn.

* Ensure that each fuel injector is connected to the proper fuel injector harness connector. Refer to Engine Controls Schematics ((L99/LS3)) See: Powertrain Management > Electrical > Engine Controls SchematicsEngine Controls Schematics ((LSA)) See: Powertrain Management > Electrical > Engine Controls Schematics

* A high resistance condition on any fuel injector control circuit can cause an engine misfire P0300-P0308 DTC to set without setting a fuel injector circuit P0201-P0208 DTC.

* A high resistance condition on any ignition control (IC) circuit can cause an engine misfire P0300-P0308 DTC to set without setting an IC circuit P0351-P0358 DTC.