F-250 misfire under acceleration
 

Hey guys, I am trying to help out a friend who's vehicle is having issues. The vehicle is a '99 F-250 (I believe its a super duty) with the 5.4L motor. He is complaining that it stutters intermittently under acceleration. I put an OBD-2 scanner to it and came back with misfire codes for 3 seperate cylinders. The thing that stood out to me from the freeze frame data was that it listed the RPMs as 0. I haven't gotten a good chance to look into this, but based off of the RPM reading, my first guess was possible Crank Position Sensor. I don't have access to a repair guide, but may convince my bud to buy one. Can somebody tell me where that sensor is located and the test procedure? or if you have suggestions on a different direction to go in. Sorry about the limited info, and thanks for any help you can give.

Just had the same complaint from my neighbor with a 4.6 liter F-150. The 5.4 and 4.6 are known to have coil pack issues which is what his problem was. He wanted me to tune it up while I was under the hood too. All I can say is YUCK...that is a real pain in the @ss truck to put plugs in. Good luck!

Thanks Mr. Shamrock! I saw that there had been a TSB about the coil packs, but didn't have the full access rights on the site I saw it on to read the whole thing. Any suggestions on a check/repair proceedure? I'll try to research it some more now that I have this clue to follow.

Anytime we get a Ford in here with misfires due to coils, we recommend ALL of them-think about it.They have all been subject to the exact same stresses and it just makes sense that when one goes out the rest are going to follow one at a time. Very rarely do they only fail with just one or two. Especially if the owner has left the OE plugs in it for the "recommended" mileage interval-that 100K is for "Normal" driving, and her are about 4 counties in Arkansas that would be considered "normal operating conditions". Every where else its too wet, too dry, too dusty, gets too hot, gets too cold, has excessive traffic-you get the picture. the 100K mile service intervals are for marketing, and the real world is that plugs need changed closer to 60k miles to keep from-you guessed it-keep the ignition coils from being overstressed due to the spark plug porcelain becoming "Domed' and causing higher secondary resistance.