P0300 Random/Multiple Cylinder Misfire Detected

I have a 2000 Cavalier 2.2L that has logged the following code, P0300 Random/Multiple Cylinder Misfire Detected. When it misfires it lights up the traction control icon and the radiator fan
comes on...(for a short while)
I tried fuel injector cleaner and changed spark plugs and both coils...wires are okay.
anyone that can help would be great!
thanks
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First you have to find out if it's all cylinders that are misfiring or only one. If it's all cylinders, start by checking the fuel system. If it's one cylinder, check that cylinder for spark, if no spark fix problem. Check cylinder for fuel, maybe as simple as it was for me, run car for a second or two, pull plug and smell for gas. If no fuel check injector, if okay, check wires to injector. One should be constant 12V while key in run, the other pulses to ground while engine cranking or running. If no 12V, check wires, if no ground pulse then check wires. All wires okay, check computer.
As some may remember, I just went through this with my Monte. Turned out to be a corroded lead for one of the injector drivers in the PCM. But I easily connected my car to the laptop, found that cylinder number 5 was misfiring.
Steve

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Somewhat ignore my previous post.
Check fuel system for correct pressure or contaminated fuel. Check ignition system for proper output. ALLData says it has to be something that effects the whole engine, so - fuel supply system, air supply system and electrical supply system, check them all.
Steve

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Thanks for the reponse... I will ran out all my fuel before making any other things to it.. pretty sure I have bad fuel..if not i'll try your suggestions.
thanks again

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