Random misfire after new spark plugs and wires

First you need to determine what type of miss you have. Is it random on all cylinders, or is it restricted to one or two cylinders? Random misfire can be caused by crank or cam sensors that are starting to give out. Single cylinder misfires can be due to plugs, wires, coils (you already addressed those), as well as internal issues such as burnt or broken valves.

P0300 multiple misfire
P0302 misfire cylinder 2
P0306 misfire cylinder 6

P0300 is random misfire code P0301 would be cyl # 1 etc.
With the odb2 scanner at erase codes turn the engine off. With the key in the run position erase the codes. Run the diagnostics again. If you still have P0300 code Check the plug wires. Loss of compression will cause misfire but it would not be random.

Check spark plugs and look for crack or melted plug wire change cap rotor new plugs one might be cracked if already replaced also fuel filter might be plugged if still happening get Haynes book do spark test on cylinders and compression test to narrow down problem but try complete tune up first before assuming the worst k

ENGINE MISFIRE

There are few possibilities that can cause engine misfire issues. It can be issue with spark plugs or faulty spark plugs. Also get the compression test done for cylinders. If any of cylinder shows low compression then required, then that particular cylinder will cause misfire.

Also get obd codes scanned, the error code will let you know which cylinder is misfiring or all cylinders are misfiring.

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For your trouble shooting I suggest you to refer the help oinks below. It has step by step details for many engine misfire issues.

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Click the link below:-----

Ford Explorer Cylinder Misfire?

http://whoisbyme.blogspot.in/2012/06/ford-explorer-cylinder-misfire.html

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Engine Misfire codes on Chevrolet Malibu?

http://schematicsdiagram.blogspot.com/2011/12/engine-misfire-codes-on-chevrolet.html

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Cylinder 6 Misfire?

http://howtobyme.blogspot.com/2011/12/cylinder-6-misfire.html

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Misfire on cylinder 4?

http://schematicsdiagram.blogspot.com/2011/12/misfire-on-cylinder-4.html

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While stop engine idles like cylinder missing?

http://schematicsdiagram.blogspot.com/2012/01/while-stop-engine-idles-like-cylinder.html

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Ford Explorer 5.0L: Engine Miss?

http://whoisbyme.blogspot.in/2012/06/ford-explorer-50l-engine-miss.html

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Oil on spark plugs and car misfires?

http://technoanswers.blogspot.in/2012/02/oil-on-spark-plugs-and-car-misfires.html

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Can cylinder misfire Damage the Catalytic converter?

http://schematicsdiagram.blogspot.in/2012/02/can-cylinder-misfire-damage-catalytic.html

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Car misfires and error code P0306 and P0303 is shown?

http://technoanswers.blogspot.com/2012/01/car-misfires-and-error-code-p0306-and.html

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Chevrolet K1500 No spark, random misfire

http://repairhelpcenter.blogspot.com/2012/11/chevrolet-k1500-no-sparkrandom-misfire.html

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2004 Ford F150: Engine Misfire and Lean Code?

http://whatisbyme.blogspot.in/2012/05/2004-ford-f150-engine-misfire-and-lean.html

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1995 Toyota LS: Misfire at idle or low RPM

http://whatisbyme.blogspot.in/2012/04/1995-toyota-ls-misfire-at-idle-or-low.html

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Toyota Corolla: Random Misfire?

http://technoanswers.blogspot.in/2012/04/toyota-corolla-random-misfire.html

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2006 Ford Freestar: Misfire on Cylinder Number 2?

http://whatisbyme.blogspot.in/2012/06/2006-ford-freestar-misfire-on-cylinder.html

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This will help.

Thanks.

change the spark plug and then the coil, if it still misfires, it is the injector what you should do first, move the spark plug from that cylinder to another one, and use a scanner to see if the misfire follows to that cylinder, if it doesn't then your problem is in the coil/spark plug wire, and if a new set still does that, your injector on that cylinder is partially obstructed.

These codes are for random misfires,but without the car actually running rough the best advice i can give you is to try a new set of spark plugs and spark plug wires,they may be failing randomly and then working again fast enough to set codes but are noticeable to you.

P0300 Random Misfire

Misfires can be caused by worn or fouled spark plugs, a weak spark (weak coil, bad spark plug wire), loss of compression, vacuum leaks, anything that causes an unusually lean fuel mixture (lean misfire), an EGR valve that is stuck open, dirty fuel injectors, low fuel pressure, or even bad fuel.

A Random Misfire code usually indicates a vacuum leak or bad gas.

NOTE: If a misfire in a specific cylinder should lead you to check the spark plug, fuel injector and compression.

I had a problem with a chevy with random misffires on all cylinders. It was the computer. Fords have very few problems with there computers. Does the check engine come on? Maybe have it scanned. 

P0300 is a random misfire code, if you are not mechanically inclined the first thing i would do if you havent done so in the past year or more, is change the plugs and wires, a random misfire code can be caused by worn plugs and/or wires not firing properly. let me know if that fixes it.