Check Engine light on AGAIN!

P0303 ignition misfire on cylinder #3.
Possible Causes:

1.Fuel injectors, related wiring, sensors, computer issues
2. Running out of gas, or poor fuel quality
3. Evaporative emissions system (EVAP) concerns: fuel vapors leaking into engine
4. Incorrect Fuel Pressure
5. EGR system concerns: leaking EGR valve or restricted ports
6.Base engine concerns: low compression, valve train problems and timing issues
7. Ignition system concerns including, but not limited to:
Faulty spark plugs
Faulty coil or related wiring
Ignition module or related wiring issues
Ignition related sensor faults or wiring issues

You will have diagnose each element until you find root cause.
And it could be more than one element faulting out.
You

PO301 & PO 303 are cylinder misfire in the cyclinders
indicated by the codes last number #1 & #3

Spark Plugs get replaced every 3 years or so & have
nothing to do with resolving any misfire issues, unless
they were in the motor for 80,000 miles & worn out

Spark Plug wire easily last 12 to 15 years or more &
usually only fail because they are mishanded & too often

You problem IF the codes are correct & they are not all the
time,is a bad ignition module or individual coil if that is
what you have

P1354VVT System Malfunction (Bank 2)

• P0300 Random/Multiple Cylinder Misfire Detected
• P0301 Cylinder 1 Misfire Detected
• P0302 Cylinder 2 Misfire Detected
• P0303 Cylinder 3 Misfire Detected
• P0304 Cylinder 4 Misfire Detected
• P0305 Cylinder 5 Misfire Detected
• P0306 Cylinder 6 Misfire Detected
• P0307 Cylinder 7 Misfire Detected
• P0308 Cylinder 8 Misfire Detected

Probably bad plug wires. Start there and then disconnect the battery for 5 minutes reconnect and start engine to see which codes have cleared.

Plugs get changed at 70,000 miles
I would suggest that you use the OEM
Plugs,they are made by NGK and are special
on my 2004 LS,I don't know about yours.

Clean the MAF Sensor with the CRC Product
for that

Change the 2 front O2 Sensors at 100,000 miles

Check fuel pressure at the fuel rail on engine

The coil you replaced on #6 ,even though you
have a PO306 Code,doesn't mean that was the
bad one. It is a COP Coil or Ford thing, you will
learn as you get involved with them

In some cases, you buy 1 new coil and walk it
from one cylinder to the next.

On single coil codes, you may get lucky,on multiple
codes or a really bad coil you won't

Your not using any fancy test equipment and
unfortunately a lot of repair shops have it and
don't know how to use it,including dealers

V6 or V8 ?

Not knowing what you have done and when, below are the normal intervals for Checks and Replacements:
If you have not done something in a while, or can't remember when it was done: go ahead and do it now to keep your vehicle on schedule.
Every 250 miles: (Every Week)
Check Automatic Transmission Fluid Level.
Check Battery Electrolyte Level, Post and Connections
Check Brake Fluid Level.
Check Engine Oil Level.
Check Engine Level + Reservoir
Check Horn Function.
Check Operation(s) of ALL Lights.
Check Power Steering Fluid Level
Check Tires and Air Pressure Levels (Don't Forget the Spare)
Check Windshied Fluid Level
Every 3,000 miles: (Every 3 to 4 Months)
Change Oil and Filter.
Every 7,500 miles: (Every 6-months)
Rotate the Tires.
Check and Clean Battery
Check Cooling System Hoses & Connections for Leaks & Damage,
Check the Exhaust System.
Check the Condition of All Vacuum Hoses & Connections.
Check Wiper Blades. Replace if needed.
Check for "play" in Steering Linkages and Balljoints.
Every 9,000 miles: (Every 9-months)
Check the Brakes: Pads, Rotors, Calipers and Hoses.
Lubricate the Tie Rod Ends and Ball Joints.
Check the Drive Axles, CV Joint Boots: Inner and Outer.
Check Suspension: Coils, Struts and Shocks.
Every 15,000 miles: (Every Year)
Replace Air Filter
Change Automatic Fluid and Filter.
Check Fuel System Hoses & Lines and Connections.
Check Drivebelts/Surpentine Belts.
Every 30,000 miles: (Every 2-Years)
Drain and Replace the Engine Coolant Fluid
Flush Coolant System.
Check and Replace PVC Valve.
Replace Spark Plugs.
Replace Ignition Wires
Check Distributor/Electronic Ignition Coil.
Check Operation of ALL Seatbelts.
Check EVAP Emission System Hoses and Connections
Every 60,000 miles:
Replace Fuel Filter.

Let me know if this helped, or if you have any additional information or questions. Contact me at FixYa.com!

Not knowing what you have done and when, below are the normal intervals for Checks and Replacements:
If you have not done something in a while, or can't remember when it was done: go ahead and do it now to keep your vehicle on schedule.
Every 250 miles: (Every Week)
Check Automatic Transmission Fluid Level.
Check Battery Electrolyte Level, Post and Connections
Check Brake Fluid Level.
Check Engine Oil Level.
Check Engine Level + Reservoir
Check Horn Function.
Check Operation(s) of ALL Lights.
Check Power Steering Fluid Level
Check Tires and Air Pressure Levels (Don't Forget the Spare)
Check Windshied Fluid Level
Every 3,000 miles: (Every 3 to 4 Months)
Change Oil and Filter.
Every 7,500 miles: (Every 6-months)
Rotate the Tires.
Check and Clean Battery
Check Cooling System Hoses & Connections for Leaks & Damage,
Check the Exhaust System.
Check the Condition of All Vacuum Hoses & Connections.
Check Wiper Blades. Replace if needed.
Check for "play" in Steering Linkages and Balljoints.
Every 9,000 miles: (Every 9-months)
Check the Brakes: Pads, Rotors, Calipers and Hoses.
Lubricate the Tie Rod Ends and Ball Joints.
Check the Drive Axles, CV Joint Boots: Inner and Outer.
Check Suspension: Coils, Struts and Shocks.
Every 15,000 miles: (Every Year)
Replace Air Filter
Change Automatic Fluid and Filter.
Check Fuel System Hoses & Lines and Connections.
Check Drivebelts/Surpentine Belts.
Every 30,000 miles: (Every 2-Years)
Drain and Replace the Engine Coolant Fluid
Flush Coolant System.
Check and Replace PVC Valve.
Replace Spark Plugs.
Replace Ignition Wires
Check Distributor/Electronic Ignition Coil.
Check Operation of ALL Seatbelts.
Check EVAP Emission System Hoses and Connections
Every 60,000 miles:
Replace Fuel Filter.

Let me know if this helped, or if you have any additional information or questions. Contact me at FixYa.com!

There are several possibilities.
Based on the year (2002) and low miles (19,000) it probably has the original Plugs, Wires and Coil. Rubber insulation on Wires does dry rot over a period of time. Spark Plugs should be changed about every 3 to 4 years regardless of miles. Wires should be replaced every other Spark Plug change. Translated you should be on you 3rd set of Spark Plugs and 2nd set of wires.
When working in the engine compartment and with the electrical system remember: ther is 40,000 to 75,000 volts present. Bad Wires could mean an electrical shock!
You can cheaply purchase Ignition (Spark Plug/Wire/Coil) Test Kits at most auto parts stores or even at Harbor Freight.
1) Remove the #2 Wire connection to the #2 Coil position.
2) Insert the tester into the #2 Coil position. Clipping the other end onto the engine block or onto a good ground.
3) Start the Engine.
4) You will be looking for a good strong (blue) and rhythmic spark. If it is not strong (yellow or orange) nor rhythmic, the Coil is malfunctioning and should be replaced.
5) If it is a good rhythmic spark, Turn OFF the Engine.
6) Disconnect the Tester and reconnect the #2 Wire to the #2 Coil position.
7) Disconnect the #2 Wire from the #2 Spark Plug.
8) Connect the Tester into the end of the #2 Wire. Clipping the other end to the engine block or a good ground.
9) Start the Engine.
10) Again you are looking for a strong (blue) and rhythmic spark. If is not strong (yellow or orage) and rhythmic, the Wire is bad and should be replaced. Wires should always be changed as a Set is the standard rule.
11) If it is a good rhythmic spark, Turn OFF the Engine.
12) Remove the #2 Spark Plug out of the engine.
13) Check the Igntion end of the Plug for carbon, dirt, or being fouled. Check the Gap.
14) Insert the #2 Spark Plug back into the #2 Wire.
15) Using the Spark Plug Tester. Connect the Tester to the #2 and clip the other end to the engine block or a good ground.
16) Start the Engine.
17) Once again you should be checking for a strong (blue) and rhythmic spark. If it is not strong (yellow or orange) nor rhythmic, the Spark Plug could be malfunctioning.
18) Clean the #2 Spark Plug.
19) Regap the #2 Spark Plug.
20) Retest the Spark Plug.
21) If there is now a strong (blue) and rhythmic spark, then the #2 Spark Plug is now good.
22) If there is not a strong (yellow or orange) nor rhythmic spark the #2 Spark Plug is malfunctioning and needs to be replaced. Again the standard rule is to replace the Spark Plugs as a set.

The several other possibilities relate to sensors. However without additional error codes or the check engine light on, we will assume that the problem can be solved with the solution above.

Let me know if this helped, or if you have additional information or questions. Feel free to contact me at FixYa.com!

I had the same problem with a 2004 LS. I took it to the dealer and turned out that 6 ignition coils were out and was factory defect. Ford extended the warranty for the ignition coil. All work and parts "no charge" this service was done about a month ago

without a fault code its impossible to diagnose. try pep boys or aamco or auto zone they will pull the code for you, usually for free. The code will relate to a sensor or area to be fixed. This will save you money and needless parts . post the code or codes so we can help

I went thru this on my 2002 LS as well.
I replaced one ignition coil at the dealer - only to get the same misfire code on another cylinder. After a little research found out is actuall a gasket/o-ring problem design of the block. Spark plugs are deep in the block - under the oil - which is why they are supposed to last 100,000 miles. But the o-rings start to leak some where between 65k-85k miles. Coils go bad because of oil contamination. If you don't solve leaking oil problem will have to replace coils again - but sooner - because leaking oil will be progressively worse.
Cost - 8 ignition coils
set of spark plugs (who knew they were that expensive
and a ton of cash for the labor to tear down the top of the motor