New to the group. This appears to be a fantastic forum. I have read the newbie section and there's alot of talk about the IAC, which may or may not be my problem. Anyway, a bit of background: I just bought a used 2002 F-150 from the local Ford dealer this past Thursday. It's a 2WD, extended (Supercrew?) cab, long bed, 58,000 miles, with the 4.6L V-8. It appears to have been kept very well by the previous owner and I really like it thus far. There appears to be a problem, though, that concerns me, and I'm not sure if this is normal or something I should have looked at.

Like I said, I bought it a few days ago. Ran great. Drove the you-know-what out of it and no signs of trouble at all. Later that evening I took it in to have the factory cassette replaced with a new CD player. Drove it alot later that evening after the CD player was put in and no problems whatsoever. Didn't drive it the next day. Saturday, it starts running rough and idling rough, though not always. This happens while driving and at idle, though it never seems anywhere bad enough to kill the engine. The "Service Engine Soon" light eventually came on and stayed on. I read in the owner's manual that when the battery is disconnected that the computer has to "relearn" idle and fuel settings. It even has a sequence for helping it do this, and I seriously doubt it had been done properly by the CD installers. Since I'm sure they disconnected the battery when they installed the CD player, and it seemed fine before that, I thought this would be my problem. So, in the afternoon I disconnect the battery again and go through the proper sequence. Take it for a drive of 18 miles and it seems better. Much better, but not quite perfect. I figure it needs more time to relearn, so I blow it off. Later in the evening I go for another drive and it starts doing it again, and the "Service Engine Soon" light comes on again. What's up?

Keep in mind that it seems very intermittent. Sometimes it idles and accelerates and drives just fine, other times it's rough and acceleration is slower than it should be. The warning light stays on. The manual also says it could be bad fuel, or water in the fuel, who knows. Should I keep driving it and let it work itself out, or will it not likely work itself out? I've read that dealers will say it's normal to do this and it'll fix itself, but then I don't always trust what they say. I'd like to hear from an experienced F-150 owner or two. Thanks.

 

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I have done some further research. I went to Autozone and "rented/borrowed" an OBDII device. I come up with two codes.


PO301-Cylinder no. 1 misfire detected
PO316-something about detecting a misfire in the first 1000 rpms, I think

Not trying to sound too naive, but what should be my first course of action, know that I know these codes? Also, I erased the codes. Is that a good idea? I wanted to see if they would come back.

One more thing, while driving home from Autozone I had the cruise control on at about 60mph and while climbing a small hill the "Service Engine Soon" started flashing, and continued to flash for about 30 seconds to one minute after I peaked the hill and turned off the cruise control. Is that anything extra to be worried about, or probably just part of the same problem. It did downshift right before it started flashing.

 

Welcome to FTE

The P0301 is what you should be working on fixing. If it still has original spark plugs replacing them would probably be a good place to start.
The next likely suspect would be a bad COP ( Coil On Plug). On these engines each spark plug has it's own coil sitting on top of it. They do go bad sometimes.
You can try swapping the COPs on cylinders 1 & 2 and see if the code follows. Drive the truck long enough for the Check Engine light to come on again and then get it rescanned. If you then get a P0302 that would mean that the problem followed the COP so the COP is probably shot.

 

Thanks for your help. I went ahead and replaced the #1 plug and COP w/boot. The plug was wet around the threads. I blew out the plug well with a computer air spray can, but I don't know if it left some moisture in there when I took the plug out or if it was maybe gasoline. Didn't have a gasoline smell. Anyway, that seems to have solved the problem. Took it for a test drive and it was a pleasure. I bought 8 plugs and plan to do them all since it's almost at 60,000 miles anyway, but had limited time and light tonight and wanted the problem fixed at least.

 

Good to hear that you got it figured out
Have you read the spark plug replacement how-to near the top of the forum?
You'll find some good tips in there.

 

Yes, I did. In fact, I printed it out and had it with me. Very informative and helpful. Even simple things like which size socket to use are very handy and appreciated. Turns out the #1 plug is very easy to get to, but I can see where some others wouldn't be.

Too bad engines can't be as simple as the '65 Chevy straight-6 I have. I could crawl in there, close the hood, and take a nap if I wanted to.