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davehop, Ford Technician
Category: Ford
Satisfied Customers: 1291
Experience:  Fully certified in all phases of automotive repair as recognized and certified by Ford Motor Company
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1998 ford f-150: check engine light..misfire on cylinder 1..coil pack

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1998 ford f-150. check engine light on. diagnosed as misfire on cylinder 1. changed spark plugs and spark plug wires and coil pack. the problem persists. good and equivalent compression on all cylinders. replaced fuel injector on cylinder 1. check engine light came back on.
Hello and welcome to JA, what size engine do you have in your F 150, I am guessing a 4.9L due to the fact that you have plug wires.
Customer: replied 7 years ago.
yes I have the six cylinder model. It has 186,000 miles on it
Did you use a coil pack from a ford dealer or an auto parts store?
Customer: replied 7 years ago.
I do not know what brand of coil pack they put on; however, after that didn't fix the problem and they decided to replace the fuel injector they put my old coil pack back on to save me some money.
Ok, here is my suggestion to you, the pcm fires 2 cylinders at a time on this engine, and we are only missing on one cylinder, so we can rule out a wiring concern and the pcm, having replaced the plugs and wires, we assume they are ok, that leaves 2 things, the injector, which I highly doubt was bad, and the coil pack, which i am sure is bad, but they must have installed one from an auto parts store, which have been known to be bad right out of the box, go to a ford dealer and buy a new coil pack and the problem will be fixed. I see this all the time, the aftermarket parts are not made to the standard that the factory parts are, and you get what you pay for. Get a new coil from the dealer, it will be fixed.
davehop and 2 other Ford Specialists are ready to help you
So was I correct?
Customer: replied 7 years ago.
A new coil from Ford was installed. I drove the truck for about 120 miles over two days and the check engine light came back on. I haven't had the code checked again but it feels like the same thing.
Let me know the exact codes you get, not just the definition, but the actual numbers.
Customer: replied 7 years ago.
The code after replacing the coil was 301
after replacing the coil, did the truck run better and then eventually the roughness returned along with the check engine light?
Customer: replied 7 years ago.
Maybe a little better. It runs rough at about 40-45 mph but idles and runs smoothly otherwise. The check engine light will flash off and on for maybe a minute every couple of days and just stay on constantly the rest of the time.
What type of plugs did they put in it? And are they properly gapped?
Customer: replied 7 years ago.
Motorcraft Platinum / agsf 34fm
I assume that they are gapped properly. This was done at a large, reputable, and well established shop.
I would check the #1 spark plug just to be on the safe side, for only the #1 cylinder to be missfiring, we need to look more closely at the components that are on that cylinder, new injector...check, new coil from ford...check, new wires...check, possible cracked porcelin on plug or gapped wrong...??
Customer: replied 7 years ago.

what is the proper gap?
.052 to .056" just double check the sticker under the hood on the fan shroud. And inspect the plug closely and see if there is a crack anywhere in the porcelin(white part). If it seems ok, lets try to swap the #1 plug with the #2 plug and see if the missfire follows it, also if it stays on #1, try a wire swap they are the same length.
Customer: replied 7 years ago.
I took the truck to the local Ford dealer. He said he thought that the ofego ports were plugged up. He removed the upper intake and found that the ports on all but cylinder #1 were completely blocked with carbon. He cleaned them out and now the truck runs fine and no check engine light! So I guess there was nothing wrong with the coil, plugs or spark plug wires.