A P0303 code means that the the car's computer has detected that one of the engine's cylinders is not firing properly. In this case it's cylinder #3.
A code P0303 may mean that one or more of the following has happened: * Faulty spark plug or wire * Faulty coil (pack) * Faulty oxygen sensor(s) * Faulty fuel injector * Burned exhaust valve * Faulty catalytic converter(s) * Running out of fuel * Poor compression * Defective computer If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back. If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.
My chilton's manual says # 3 misfire. Good luck.
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The 2003 Ford Mustang Owner Guide shows ( 5W-20 )
The 2000 Ford Mustang owners manual shows headlight bulb ( 9007 )
I have a ScanGuageII in my 2014 Mustang GT and it shows that I have gone 145 MPH when the computer shut it down.
www . motorcraft . com ( no spaces ) shows : Ignition timing ( 10 degrees BTDC ) for a 1988 Ford Mustang 5.0 L unless engine decal shows different
The 1998 Ford Mustang owners manual shows : WITH FILTER CHANGE - 4.7 liters ( 5 quarts )
The 1998 Ford Mustang owners manual shows ( 5 quarts ) WITH FILTER CHANGE
For the 2005 Ford Mustang 4.6 L - 3V engine : The owners manual shows .040 to .050 inch , but www . motorcraft . com ( no spaces ) shows .054 inch and shows that the website is updated daily
The 2005 Ford Mustang owners manual shows : " shaker 500 - audiophile in - dash six CD / MP3 sound system "
The 2005 Ford Mustang Owner Guide shows " regular " unleaded , 87 octane for the 4.6
AverageJoeResto.com has a resources section that shows paint chip colors and codes, there are more codes under the data plate decoding page. Check it out I'm sure that you will like it.