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P0303 cyl #3 misfire code driving me crazy

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Old 03-29-2011, 11:44 AM
Join Date: Feb 2010
Posts: 30
P0303 cyl #3 misfire code driving me crazy

I have a obd2 P0303 cyl #3 misfire code ,changed plugs,changed wires ,swapped coil temporarily for one i know is good , this is on V-6 auto continuous check engine flashing- car runs fine drives good then irradic idle and will stall in gear. At other times it runs and idles smooth? changed IAC , still the same ,checked for vaccuum leaks can't find any?
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Old 03-29-2011, 12:27 PM
Technical Article Contributor
Join Date: Oct 2005
Location: MI
Vehicle: 1998 Ford F150 5.4L 4X4
Posts: 25,636
Flashing MIL means just one thing, - she's missing. Fuel first, then ignition. Change the Fuel filter lately ? What's the pump pressure reading?
Windsor Built 5.4L, E40D, Transgo kit, 9.75 Rear gear, Brembo rotors, Carquest Blue's, Bilstein's, Ported & Polished Intake/TB, Denso Iridium's, Pace setter LTH's, Magnaflow HFC's, Magnaflow 20X9X2.5 HF Muffler, Type 3 19lb Injectors, Volant Intake w/Amsoil EEA191 Filter, 265/17 GY Fortera's.

Compression Testing Procedure
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Old 03-29-2011, 04:23 PM
Join Date: Mar 2011
Location: Low Country, South Carolina
Vehicle: 2000 Ford F150
Posts: 39
Mine did this too except im a 5.4L. When she is missing on one cyl the truck idles a little rough but will not stall. Once I changed the coil and plug she runs smooth but when i pull up to a stop light the idle will jump and fall and eventually the engine would die. This went on for a month or two until the coil fouled out again so i havent done anything to fix it yet. There is a grounding wire that screws into the fire wallthat let the water drain in and drip down on top of the COP that i have fixed with a lil silicone. I would rather it always run a lil run rough than cut off on me every time i stop so i havent replaced the COP.
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Old 03-30-2011, 12:40 PM
Join Date: Feb 2010
Posts: 30
it has about 30psi on the fuel rail , could a single bad/clogged injector be causing the problems? is 30 psi enough or is there a fuel pump problem ? thank you in advance for any help
cwthill-:-craig hill central,Florida 97 f150 4.6L, 4r70w, 3:55ls,stock,cold air intake,pioneer 6 disc,285/mickey thompsons on rear

Last edited by cwthill; 03-30-2011 at 12:42 PM.
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