First off, did you run out of gas recently? If you did, then this will throw the P0300.
If not, here is some info from the Ford Technical Service Publication CD for P0300:
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HD1 CHECK POSSIBLE CAUSES TO MISFIRE
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Misfire Continuous Memory Diagnostic Trouble Codes (DTCs):
P0301 - Cyl #1, Inj Test Pin 75
P0302 - Cyl #2, Inj Test Pin 101
P0303 - Cyl #3, Inj Test Pin 74
P0304 - Cyl #4, Inj Test Pin 100
P0305 - Cyl #5, Inj Test Pin 73
P0306 - Cyl #6, Inj Test Pin 99
P0307 - Cyl #7, Inj Test Pin 72
P0308 - Cyl #8, Inj Test Pin 98
P0300 - multiple cylinders misfiring, or cannot identify cylinder due to Camshaft Position sensor failure.
Possible causes:
-- Ignition System.
-- Fuel Injectors.
-- Fuel Pressure.
-- Evaporative System.
-- Canister Purge.
-- Base Engine.
-- Running out of fuel.
NOTE:
Running out of fuel may turn on the MIL and possibly store a Continuous Misfire DTC.
* Has the vehicle recently run out of fuel?
Yes
OBD II system OK. COMPLETE PCM RESET to clear DTCs (REFER to Section 2A, «Powertrain Control Module (PCM) Reset»). RETURN vehicle to customer.
No
GO to «HD2».
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HD2 CHECK FOR OTHER CONTINUOUS MEMORY DTCS
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NOTE:
Check for other Continuous Memory DTCs which could cause the misfire DTC.
Possible causes:
-- Camshaft Position Sensor (CID).
-- Octane Adjust (Oct Adj).
-- Ignition Coil Primary Circuit.
-- Knock Sensor (KS).
* Are there any other Continuous Memory DTCs present?
Yes
ADDRESS the next Continuous Memory DTC. DISREGARD Misfire DTC at this time. GO to Section 5A for «Powertrain DTC Charts».
No
GO to «HD3».
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HD3 CHECK FOR ON-DEMAND SELF-TEST DTCS
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NOTE:
Check for any key on, engine off DTCs which could cause the Misfire DTC.
* Are any Key On Engine Off or DTCs displayed on the Scan Tool?
Yes
GO to Section 5A, «Powertrain DTC Charts», and PROCEED as required.
No
GO to Pinpoint Test Step «JB1» to evaluate spark plugs and secondary wires. If OK, GO to «HD4».
