I have a 1997 F150 4.6L 4X4. When I fire it up it runs great until it reaches running temp and then it runs rough and engine light flashes. I just took it for a hard spin uphill and it seemed to go away. This happens on occasion. Seems fine for awhile but comes back. Trucks broke and so am I. Any suggestions would be appreciated

 

You know what, I have the same truck as you. I've been poking around various posts and have noticed over the past few days a rash of similar check engine lights. The cold and moisture are really paying a toll.
Mine threw out a code for the number 6 spark plug. I went to my local Auto Zone and I live in a small town. What would the chance of 2 other guys there with the exact same truck with the exact problem. (well one was the 5.4). but never the less, the moisture factor really has to be considered. I reset my code knowing that i would have to replace the plugs and have not had a problem since. So..was it moisture? I'll change the plugs to be safe though
You say your truck is now broke? do you mean it will not run?
If you can just zip it to a local auto parts , most now a days will check your code for free.
At least you will know what your looking at. Going by my encounters over the past couple days....I wouldn't be surprised it is a code for a spark plug misfire detection......

Just be careful , don't go old school and just replace plugs wires, filters, etc....because with the computers in the vehicles now, it is rarely those things anymore.
It's funny, if you have a vehicle under warranty and you took it to a dealer an d they found a plug was bad...they will only replace the one plug even if you were higher in milage....
You also said you were broke too...
So, if all your budget allows is one plug...in theory...that is fine for now!

 

If you are having moisture caused misfires on a 4.6L, then I would suspect the plug wires. Make sure to put plenty of dielectric grease on the plug boots to seal them.
On a 5.4L or 4.6L with COP's, I would start by replacing the COP boots, also appliying ample dielectric grease.

 

Thanks for the info. I guess I'll try the plugs first. I remember it did it to me about 6 months ago and it was the #7 cylinder as I recall. Replaced plug and ran fine till now. Have to go to up north tomorrow and don"t want to have problems on the road. But why does it run good till it gets to running temperature?

 

Not too certain exactly. I would assume the computer riches and leans fuel mixture and does the same at different operating temps. (Like a choke on old cars in the cold).

Also, if there is moisture near contacts, it could be basically "Ice" and as it warms up...water. Once it is water, it may be easier to get up into the wrong spaces.

Good Luck.

 

bc, you gave a signiciant clue.

Light flickers.
That is a sign of a plug not firing.
This allows to much raw fuel to get to the cats.
May be a coil pack, may be a plug, may be a wire or two or more of same.
Could be a coil pack goes bad when the engine bay heats up.

 

Thank you all. I really enjoy this site when it comes to my truck problems. I have read alot of other posts about this problem and there sure is alot of good advice. I lost my Haynes manual in a recent move and it sure is nice to have some sort of idea what the causes could be. If I have to take it into a shop, I feel that I they might think I know what I'm talking about and I may not get screwed in the pocket. THANKS AGAIN!