Code weirdness help and other advice requested

Cliff Notes:
Why would a cyl 1 misfire (P0301) code show up after a cold start, then go away after a 5-10 min drive?

Details:
So, I got a code scanner when my car had a "service engine soon" light and a miss or other intermittent rough-running/hesitation.

I found only a P0301 (misfire, cyl 1) code and checked. Sure enough water was in there and the connection was very corroded. I cleaned the COP and swapped it with cyl 5's COP. Then cleaned in there with the clean cyl 5 COP and some electrical contact cleaner (series of insert on spark plug, removal, clean COP connection, repeat) and re-assembled everything.

I have driven it ~20 miles and I just checked the Code with the reader before driving for another 5min or so. I checked before I drove for 5 min this morning (but after erasing the code I found before I swapped COPs and cleaned the connection on cyl 1 spark plug, above) and the P0301 code was back. I did not erase (a very specific procedure on this reader, which I definitely didn't do), I drove for 5 or 10 min, then checked again. I got "0 codes" that time.

I don't get it...

...Plus, anyone think continued (but much improved) rough-running/hesitation could be something besides an incomplete cleaning of that cyl 1 spark plug's connector? I have 8 replacement motorcraft platinums (these are motorcraft coppers I put in myself 8-10K mi ago), but no time right now to work on a dead-cold engine and get those plugs swapped out. Anything else you think I should do? It's a 2000 GT w/ 74K mi on the odo.

Thanks!

-Jon

Experience is a hard teacher because she gives the test first, the lesson afterwards.
-Vernon Sanders Law

joshjwc9 said:

Did you pull that plug in cylinder 1 and or 5 to compare them?

How many miles are on the plugs?

My guess is that when the corrosion happened it caused a misfire, which fouled the plug...

Let us know how your search goes! And trust me there are many strange codes that have popped up on me before!

Click to expand...

There's 8-10K mi on the new plugs.

I haven't had a chance to remove/change plugs. I have relacement platinum plugs, but don't have the time to put them in, yet. The ones in there now are copper ones I put in a while back.

I'll let you know what find when I pull the current ones.

I changed the plugs out with the motorcraft platinum ones I bought for $24, and my car runs like new, again.

I had an extended-time-to-start problem developing, and now the car starts up as quickly as it used to. Just cranks right over, now.

Look at what I took out of there:



The one on the far left is cyl4, then left to right it goes: 3, 2, 1, 5, 6, 7, 8. This is so cyl5 and cyl1 are next to each other. Nice, huh?

The Stang lives, again!

View attachment 254866