2004 expedition running rough

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mustang323258

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we have a 2004 expedition and recently it started running rough the service engine soon light came on and coded at PO300 PO301 we took it to the shop and they replaced all the spark plugs and the coil pack on cylinder one. it has new brakes,rotors, alignment and positive battery terminal. The battery is 5 years old and we are going to replace it soon. the problem is it still runs a little rough. Sometimes it seems fine and others times it doesn't. when accelerating slowly is seems like it has a vibration sometimes and other times it seems like its missing. if you come on to the gas hard it doesn't do it but the service engine light starts flashing for about 5 seconds and goes out. If it has been sitting for a few hours it will go fine for a little while before it starts doing it again. If it idles in park it idles fine but when idling in gear it seems rough at times.
 

docraymund

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You need to do a cylinder balance test. There are vids on you tube and info on other sites on how to do this.
 

Bedrck47

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P0300 - Random Misfire
The random misfire DTC indicates multiple cylinders are misfiring or the PCM cannot identify which cylinder is misfiring. Camshaft position sensor (CMP).
Low fuel: less than 1/8 tank.
Stuck open EGR valve.
Blocked EGR passages.
One or more EGR passages may be blocked or partially blocked. If this is the case the misfire detection monitor indicates the EGR port to check for possible blockage.

P030x - Misfire Detection Monitor
The misfire detection monitor is designed to monitor engine misfire and identify the specific cylinder in which the misfire has occurred. Misfire is defined as lack of combustion in a cylinder due to absence of spark, poor fuel metering, poor compression, or any other cause. Ignition System.
Fuel Injectors.
Running out of fuel.
EVAP canister purge valve.
Fuel Pressure.
Evaporative emission system.
Base engine.
The MIL blinks once per second when a misfire severe enough to cause catalyst damage is detected. If the MIL is on steady state due to a misfire, this indicates the threshold for emissions was exceeded and caused the vehicle to fail an inspection and maintenance tailpipe test.

How many miles on the Expy??
What engine do you have??
When was the fuel filter changed.
You may want to check your fuel pressure
 

Habbibie

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My 05 did everything yours did, so I gave it a full tune up (new plugs, not the coils) and that didn't help, then I replaced the coils, that too didn't help, then at that point I figured it was either the fuel injectior or an O2 sensor, I decided to do the O2 sensor cause it was a cheaper and easier fix than the injector, anyways it was the (bank 1 sensor 1) the one on the right side under the truck before the cat since all my misfire codes where on bank 1 (p0300, p0301, p0302, p0303, p0304), once I replaced it ($55 Delphi brand sensor) I turned off/erased all CEL lights and took it for a 30+ mile test drive, it ran perfect no miss fires no rough idle, actually it's been over 3000 miles since I did the repair & it still drives perfectly.

Hope this helps

Edit: mind you I never had a check engine light for the O2 sensor, it was just my knowledge in auto repairs that led me to believe it was at fault.
 
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2004XLT

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What is the mileage and recent maintenance? You're on the right track with plugs and coils. I've had to replace both of the first oxygen sensors at relatively low miles. Fuel filter is often overlooked also.
 
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