I own a 1998 Ford F-150 with the 4.6. Yesterday on my home from out of town the check engine light started to flash and then stayed on. I had the code checked today and it showed P0303 tripped twice. That means the 3rd cylinder is misfiring. I'm not sure why. It did this like six months ago but I thought it was because I washed my motor. How do I check the coil (it has only two coils)? One coil for each side. could it just be the wire?? Any help is greatly needed.....

 

I'd check the wire first,that being the least expensive solution. It is possible for one part of a coil pack to burn out, or so I've heard.

 

But How Do I Go About Checking The Coil????

 

In-line spark tester. If your coil pack is bad,they are 39.99 at Autozone. I'd still try that wire first though.

 

You don't!! If you have to ask lol .. Kidding aside , these modulars are picky when it comes to the ignition system . You can find Coil-pacs very cheap on eBay... I wouldn't screw around with the 98 , I suggest replacing both at the same time and updating your plugs and wires. The best tune up you can give the ignition system.. You won't have to worry about it after doing .

Very cheap on ebay.

 

Did the notice the engine running poorly or misfiring prior to the CEL coming on? I would swap the two coils around being sure to keep the spark plug wires in the proper position. Then, drive it for a while (at least three OBDII drive cycles) to see if the misfire changes to another cylinder. If the misfire changes positions, then it is a bad coil. If the misfire does not change to another cylinder, then you have some more troubleshooting to do.

Most coil misfires are caused by breakdown of the coil insulation under high voltage conditions. It is usually impossible to test the coils using equipment available to most do-it yourselfers. If you swap the coils around, be sure both are clean and dry when you do.

 

OK, Today I pulled the wire off and checked the resistence and it read 11.70k. I went to the parts store and checked to diff brands of wires the same length. One checked 11.22k the other checked at 1.48k. I could not believe the diff i checked them several times and got the same reading. I pulled the coil pac off and cleaned under it and put it back on. I also pulled the spark plug and changed it. Any ideas on the readings of the plug wire. I am very confused now!!!!!!!!

 

Well , sounds like you did a very wise thing checking the wires at the store. Don't buy the ones with low resistance . All your other wires test out at 11.70 (or close) as well? Did you check for spark jump -or short while running at idle in the dark..?? If all your wires check out and you checked for spark jump and didn't notice any, I would suspect there fine.. If you coat them with dielectric grease or silicon sealer that will seal and preserve them longer..

You can do the basics and clean up the coils and grease the boots and check the primary - "pacs" -when bad, It's to hard to pinpoint without a scanner with a mode 6 history reader - reads cylinder misfire history from memory.

If you go thru the wires, check out the boots then grease the insides and conclude there fine. Check your plug gaps -(plug gap increases over time, so if they have miles on them , check as well...)

You do all that, I would look towards replacing the pac/pacs..

 

Hey hey, fixed the problem...It was the plug wire, I purchased a new one from dealer for $15.00. Costed a little more but I know from dealer it's the right one......thanks guys