I have a 02screw with 5.4, yesterday I got a misfire. I know the plugs were replaced 6 months ago, but only one cop. There is no CEL, and the truck starts and idles but you can really notice the misfire under acceleration, and after the truck warms ups it gets worse. I believe it is prob a cop, but with no code to point me in the right dirrection, what is the best way to trouble shoot?

 

my 01 4.6 super crew is missing without tripping the engine light but the obd2 reader still picks up the misfire codes. my cyl 1 was misfiring so we replaced all plugs and boots and it still did it so we swapped the coils between cyl 1 and 3 and the miss moved to cyl 3 so i think the problem may be solved with a new coil to replace the one that was in cyl 1 (now in cyl 3) maybe you have a similar problem and can test the same way. symptoms are the same right down to the part of doing it only under accell and worse after it warms up. should have my new coil tonight. im just using the cheapest obd2 reader from advanced auto. it was around $30

 

I do have a code reader, but it just a cheap unit, I will look to see if shows me a misfire code, but I am not sure if it will without a cel light.

 

Power brake the truck. Hold the rpm's right where it starts to miss and don't let off, stay in it. Should set a code for you is a short period of time. Using a cheap reader won't give you mode 6 data or cylinder contribution data. GLWR