I'm getting codes for system to lean, and cylinder 6 missfire right now
the truck will stumble while cruising between 40-60mph, it's been serious enough to set off the flashing CEL a couple times now, and the problem seems to be getting worse. I've got an edge and a 3" catback on the truck now

Does anybody know where i should start with trying to diagnose this problem?

 

Might have a fouled plug if it's not kicking a code for the COP. I'd venture to guess the misfire is causing the lean condition. I could be wrong though so let's see what others say.

 

I think I am getting the same response from mine (04 5.4) When I am around 50-60Mph or when I am around 1900 Rpm it acts like it wants to stutter, I haven't hooked it to a computer yet to see if I am getting any codes. I am getting it looked at on Monday so I might be able to let you know what they say about mine.

 

i made a thread related to the stumbling before and someone suggested cleaning the mass air flow sensor.. anybody think this will work?

 

won't hurt and it's really easy to do.

 

i cleaned the mass air flow sensor, and replaced my air filter (it was pretty dirty), but the problem still persists. no CEL at the moment
any input?

 

Well after talking to a guy at work that used to have a lightning with the 5.4 in it said it was one of the coil packs which around $50, they will start going out starting at cyl 8 but I am not getting any error codes and it only does it when its warm.

 

well i have a 04 5.4 also and mine was doing the same thing when i was one the highway and cruising about 60ish i would get a bad shutter, how many miles do yo have on your truck? mine was at 100,000 when it started i tried a couple of different thinks thought it might be my tires loose and then i talked to a couple of guys on here and they said that it might be my spark plugs, i thought that wasn't the case cause i never got a code or anything, i also had a rough idle... and i went to the dealership and had them replace the spark plugs and coils and after driving it 4,000 miles these last 2 months it hasn't made a single shutter or weird vibration... so it might be that i would look into it though...

 

Change the plugs and it will go away.Mine did the same thing all i did was change plugs.Dealer said cop and that was not the case they just want your money.

 

my truck has 68k miles on it now
does anybody have the link for the TSB on changing the plugs? i'd like to try it myself instead of bringing it in to the dealer for it

 

Do yourself a favor and let a dealer do it that can tell you that they have had a high success rate.

 

i second that bud you just need to let the pro's do it, you wont regret it, it is so hard to do it yourself and then if something goes wrong or you can't figure it out you are going to have to tow your truck to the dealer.... best of luck though

 

alright i'll probably end up bringing it by the dealer then sometime next week
anybody from the ct area have a dealership that they've had success with?