Need some help fellas, misfire at startup
 

2002 F150 4.6
254K miles

At startup, I have a rough idle until the truck warms up, and then it runs fine.
I had checked the codes - number 302 and 316 came up.
I replaced the COP for that cylinder, but it's still doing it. I also aired out the cylinder well and into the plug hold, thinking there may be moisture in it.

What's my next step? gotta get the codes cleared so i can pass an inspection test (in Louisiana).

thanks as always
C

Did you replace the coil boot also? Is there power to that coil? Is there power to that injector? Did you pull the spark plug and inspect or replace it?

i replaced the entire coil/boot. no i did not pull the plug. i figured if it was fouled, there would be a consistent misfire. its only doing it when it first starts up.

of course the code 316 says "first 1000 revolutions.."

How many miles on the plugs and what brand are they?

i changed the original plugs at 100k. so these have 150K. kind of scared to change them again. can't remember the brand.

Good grief! The plugs need to be changed. Why the fear? Use Motorcraft plugs only and torque them to 28 ft lbs.

Pull the cop, stick a screwdriver or something in it, start the engine and make sure you have spark. If you do, then it's either a bad spark plug, injector issue, or a component of that cylinder is worn and doesn't make adequate compression until its warm.

If you don't have spark, it could be a bad coil, wiring issue, or coil driver in the PCM.

Holy crap. Change the plugs dude. Motorcraft only, 28 FT/LBS, no anti-seize.

just worried about breaking a plug off is all.
i'll check into it and let yall know the results.

thx for the help

That's the 3 valve engine. The 2 valve engines sometimes remove the plugs automatically.

The only way you will break any plugs for that engine is if you try to. it's the 2004-early 2008 5.4s that have the breakage issue. You just have to torque your plugs tight to keep them from spitting out. You should change the plugs as quickly as possible, you are stressing the COPs.

With that many miles, I'd change the plugs AND the COP boots/springs and throw a bottle of Techron in the gas.

You won't pass inspection till you do.

I'm having the same problem except it has all new plugs coils and injectors with less than 500 miles. Getting 301 and 302 codes that's the reason for the new parts in the first place, this set of plugs and coils had reached about 85k miles so I figured it was about time and did the injectors just to be on the safe side. I'm not really sure were to look next.

Same thing I said in post #7

Pull the cop, stick a screwdriver or something in it, start the engine and make sure you have spark. If you do, then it's either a bad spark plug, injector issue, or a component of that cylinder is worn and doesn't make adequate compression until its warm.

If you don't have spark, it could be a bad coil, wiring issue, or coil driver in the PCM.

Around 150 all cylinders. Again all new plugs coils and injectors. I have never heard of a harness going bad.