06 4x4 with 5.4l 77k miles.

I've replaced 1 coilpack about 2 years ago when it went dead and through a cel. this time no cel or codes and only does it when i'm at hwy speed between 50-70. seems to run ok below 50 and above 70. I've search the forums and found problems from driveline to bad coilpacks and injectors.

an way to tell when there is no cel what the problem could be. I haven't changed the plugs yet ( afraid to break one in the cylinder) or fuel filter. That will be my next step. I don't drive it daily, it sits pretty much in the garage 25 out of 30 days a month.


TIA.

 

the sooner u change the plugs the better. as for the misfire, does it do it during cruising rpm? or on acceleration?

i ask because mine did it during acceleration. one time i just held the rpms steady and footed the gas so it just kept shaking the crap out of the truck. eventually it threw a code for 2 misfires and i ended up changing the #2 plug. shortly after i changed all the coils for pleace of mind.

 

02sc,

when holding steady rpm's. and it is not a constant missfire. it just studders and then is ok and studders again. does it with cruise control or footing the gas. it is ok when i am wot or passing other cars. i guess i'll jump on the changing the plugs this weekend.

i'll go through the forum again on which one's everyone is using.

 

My 05 with the 25K miles and the 5.4 started doing the same thing this winter. With the cruise set it would buck and shake like crazy. Took it to the dealership and they said I had 3 out 8 plugs fried due to my K&N CAI making it run lean. They replaced the three plugs but two weeks later it started again and I took it back, they replaced the remaining plugs and I removed the CAI, have not had an issue since.

 

if you can get ur hands on a scan tool and check for codes u would know which ones are acting up. it will likely be 2 plugs, one after the other in firing order. the first one causes the misfire, the second misfire is just a direct consequence of the first one misfiring.

P.S. you dont need a CEL to have codes. the CEL only comes on when it happens so many times, you have obviously not crossed that threshold.

 

Typically your problem is plugs. Mine did the same thing at 60k, others have had it sooner, others later but the symptoms are always steady rpms, cruising speed, random stutter. At 60 my plugs were gapped so bad I was surprised it ran as well as it did. The plug change isn't that bad, I've done several sets and haven't broken one yet. You just need seafoam, a hot engine, a good penetrating oil, and patience.

 

I had this problem also but with a 98 4.6L. Had the plugs, wires, and fuel filters changed and it fixed the problem!

D

 

I'll keep beating the horse, change the plugs! Also not a bad idea to change the "boots" (cheap) either while you're there.

 

thnks for the info guys.

couple of questions though.

what "boot" are you referring to? and seafoam, is it really needed? do you add it to the gas tank and crank case, or just to the pcv valvue hose?
I have a Lisle (LIS65600) on order too. just incase!

 

Personally, I do not believe in Seafoam. If you want to run a cleaner in the fuel for a couple of tanks, get a couple of bottles of Techron. The boots are the rubber pieces that slide down over the plug insulators and hold the coil on the plug. They can crack with heat and age.

 

The spark plug boots that go on the coils.

I can't speak for the Seafoam, I didn't use it.

Good job on the tool, you MAY need it!