ok. when i first start up my truck in the morning and when i back out of my driveway my truck seems to run really rough and it stumbles. This only happens every so often. Then occasionally when i am sitting at a red light I can feel it "buck". thats the only word i can use to describe what it does. I think it is a miss-fire but it hasnt thrown a code or anything like that. This has been going on for a good 6 months. I can also feel it sometimes when i am getting onto the freeway as well. I would think that if it was a missfire then it would have thrown a code if it has been going on for 6 months or so. I also just got my A/C working again not that long ago and it seems to be even worse when i have that on. My truck is a 97 F150 with the 4.6. If you guys have any idea of what this could be i would greatly appreciate it. I am going to be leaving in about a month to go to school in Chicago and i would like to get it fixed before i go. I want to do it myself because i really dont want to take it somewhere and pay someone to fix it. I was thinking a little bit and i was wondering if it could be one of the coil packs that have gone bad. I dont know. but if any of you guys have any ideas of what it could be then that would be great. Thanks.

 

Low grade misfire. The "misfire monitor" doesn't pic this up most of the time.




Replace plugs with "Motorcraft" only.

Replace wires. ( Use Di-electric grease in the boots)

Replace BOTH Coil Packs.

That's it...

Night and day difference..