I have a '99 with a 5.4L and 108K. I replaced all the spark plugs cuz it was really rough running and misfiring. Even with new plugs it's still feels like it's missing when at idle but no misfire codes or any codes at all. And my door ajar light won't turn off. (2 totally different problems but thought I'd throw it in) any ideas?

 

sometimes its not the plugs or wires ..its the computer...i think if you take it to the shop it will read what it is ..my old one was missing and it was the intake manifold gasket it had a hole in it

 

I'd recommend you run a can of fuel system cleaner thru a tank of gas before doing anything else. A very good one sells for about $3.00 per can at Wal Mart. It's called Berrymans B-12 Chemtool. It's good stuff.