Started having a problem with my 99 F150 5.4 Supercab over the weekend. Shook at idle and power was way down on acceleration. Heck, it even shook while accelerating. Took the thing in yesterday w/ 6400 miles on it and they replaced the coil pack and she runs fine now. # 4 cylinder was not firing because of this problem. I guess I was just wondering if anyone else had experienced this problem or is it an isolated incident that I need not worry about anymore? I almost think this problem was there at the beginning now but was just very slight. It seems much cleaner on acceleration now and the occasional shudder at idle is gone.

 

Your not the only one. I was driving my '97 4.2 V-6 when it developed this misfire. Just like yours, it was there at take off, and acceleration. It never went away. They cause, a faulty coil pack. Once it was replaced, it started running like a champ.

 

HI!... RACINGVIKE when I brought my truck in for it's breakin inspection, the dealership called me and said the engine service light came on and the truck started to shake and misfire as the mechanic drove it out of the bay. They did a diagnostic on it and found that the #6 coil pack was all corroded inside and the corrosion had eatin the top of the sparkplug. The mechanic replaced the coil pack and cleaned all the others. He also put some dielectric gel on the tip of the sparkplug and inside the coil pack to help keep the corrosion at bay.

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NEAL [ the horsepower freak ] NEWMAN
'99' F-150 XLT SPORT, oxford white, reg cab shortbox stepside,5.4, auto, 3.55L.S, captain's chairs, bedliner, GTS carbon fiber headlight covers, **** CEPECK clear halogen driving lights, GTS slotted tailight covers (painted oxford white), FORD locking lug nuts, tinted windows,true duel exhaust with 2.5 inch mandrel bent pipes and FLOWMASTER 3 chamber mufflers with 3' tailpipes exiting before the rear wheel like the LIGHTNING, HELLWIG rear stabalizer bar, AUTOMETER guage pod and tranny temp guage, custom fabricated air intake trac and huge K/N filter, TPS mod, BELLTECH 2-inch rear drop, soon to be installed 4.10 gears, and just ordered my SUPERCHIP.

 

Hey Dmatlock, Are you sure they repolaced a coil-pack? I thought our 4.2 v-6 only had one main pack?? My truck is running rough at idle also.
Rich

 

Oddly enough, my #4 coil pack went bad
on my 99 5.4L. The truck shook like
an high magnitude earthquake on just 7
cylinders. The reason? Dealer said a
coolant line was not properly clamped
at the factory and coolant leaked onto
the #4 plug/coil shorting it out.

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1999 ORP SC Medium Toreador red 5.4L

 

Same problem here!
99 150 S-cab w/ 5.4.
Coolant leaking on #4 coil.
I'd think that these coils would be sealed against this kind of damage.
What about water getting in there?
Guess I won't be power washing my engine anytime soon!
BTW it still idles rough.