P0306 CODE ALSO. TRUCK WON'T STAY ON. on 2002 Ford Explorer

We have a 2002 Explorer v8 4.6L and it was working fine until it just didn't want to start and stay on about a month ago. We got te Misfire code and changed all spark plugs along with coils and booth on the 6th cylinder. Car worked for about a week and now has the same issue... What can it be? It trns on but only stays on i you keep your foot on the gas. Please help! Have tried everything

Asked by for the 2002 Ford Explorer
Look at your last sentence..."IT ONLY STAYS ON IF YOU KEEP YOUR FOOT ON THE GAS". Was it like that before you replaced all those parts for a single cylinder (#6) misfire?IF it wasn't then I'd suggest working backwards to find a vacuum hose off or a mass air flow sensor unplugged THEN if your still getting only P0306 then stick to diagnosing what's related to that cylinder Give me more input I give you more output..... IF I'm even getting you on the right track.I can help with some suggestions for things to check without a scan-tool if that helps.
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Hi This is Green's Garage answering. If you have replace the coils and spark plugs, then it may be a vacuum leak, a broken vaccum hose. We have a smoking machine to check for vacuum leaks.
Also you should check compression