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5.4L Misfire
Misfiring can be caused be many issues. Fuel filters seem to be the leading cause. Find out what other issues your truck may have to be cause these problems
Helpful Advice
Misfiring can be caused be many issues. Fuel filters seem to be the leading cause. Find out what other issues your truck may have to be cause these problems
Helpful Advice
5.4L Misfire/Hesitation Issues
#32
#33
Absolute Frustration with Misfire/Hesitation
ABSOLUTE FRUSTRATION!!! Guys I'm back to the drawing board on my truck. I've spoken to a couple of mechanics and got this blank stare from both. I've got one more to try Monday (guy I've known for years) and hope he has some idea. Everybody keeps telling me to change this and that but only because they don't have a clue what to do.
I did a vacuum test this morning and it was good and steady. Cannot for the life of me get this thing to throw any more codes. Cylinder misfires have been random (8 then 4 then 6). Due to the random nature I've ruled out fuel injector, cop or plug problem (when pulled each has been good). Fuel filter has been changed, MAF cleaned (again), PCV valve changed. Slightly rough at idle but when put in gear and driven with slight load misfires and hesitates so bad it will shake your fillings loose and still no code. Going up a hill is the roughest ride you can imagine. When there is no load it smooths out considerably.
I'm a shade tree mechanic at best but if a certified mechanic looks at me with a blank stare what the heck am I supposed to do? This truck ran absolutely great until it hit 138k miles. I know there has to be something I can do without throwing money at parts just for the heck of it.
Sorry for venting...
I did a vacuum test this morning and it was good and steady. Cannot for the life of me get this thing to throw any more codes. Cylinder misfires have been random (8 then 4 then 6). Due to the random nature I've ruled out fuel injector, cop or plug problem (when pulled each has been good). Fuel filter has been changed, MAF cleaned (again), PCV valve changed. Slightly rough at idle but when put in gear and driven with slight load misfires and hesitates so bad it will shake your fillings loose and still no code. Going up a hill is the roughest ride you can imagine. When there is no load it smooths out considerably.
I'm a shade tree mechanic at best but if a certified mechanic looks at me with a blank stare what the heck am I supposed to do? This truck ran absolutely great until it hit 138k miles. I know there has to be something I can do without throwing money at parts just for the heck of it.
Sorry for venting...
Last edited by Bigwheel; 01-15-2011 at 02:15 PM. Reason: New Information
#34
#36
#37
#38
Maybe it is the Motorcraft sparkplugs?
I put a set of Motorcraft SP-479 plugs in my S'crew two weeks ago because I was having a misfire under moderate load(highway speeds in overdrive). I believe my original problem was due to some oil spilling into the number 1 plug well - found that when I went to change the plugs. This past week I started having a more severe misfire (under light loads such as accelerating from a stop) when the truck was cold (temps were in the 20's F most of the week). The truck doesn't seem to have as much power as it did before even when it is not misfiring.
My previous sparkplugs were NGK Platinum 3403 which had about 48K miles on them and were put in with new Global cops. For the record I had one Global cop fail within six months but the others were doing fine. I'm wishing I had went with the same plugs now. The NGK's have a slightly longer insulator on top which may make a better connection with the spring and the center electrode has a much finer wire which I think fires better. I think my next step will be to try a full set of new cops just in case one is going bad. I double checked all my electrical plugs today just in case that was my problem.
My previous sparkplugs were NGK Platinum 3403 which had about 48K miles on them and were put in with new Global cops. For the record I had one Global cop fail within six months but the others were doing fine. I'm wishing I had went with the same plugs now. The NGK's have a slightly longer insulator on top which may make a better connection with the spring and the center electrode has a much finer wire which I think fires better. I think my next step will be to try a full set of new cops just in case one is going bad. I double checked all my electrical plugs today just in case that was my problem.
#39
There's just know way you could have not figured out why you truck is running this way, IF you've done everything mentioned. No way in hell.
#40
same 40 - 50 mph shutter
07 5.4 l flex w/39,000 miles
just changed plugs w/e3 a month ago and switched cop's w/GMS...
problem started Friday...pulled all GMS cop'f off and re-installed factory cop's
over the same spark plug it came from...same problem!!!
checked all cop bolts...checked all connections...cleared all old codes...
only dove it for about 10 minutes and code P 0358 came up...
is that the #8 (drivers/rear) cylinder misfire???
I need to drive more for more codes...do I need to check plugs too???
07 5.4 l flex w/39,000 miles
just changed plugs w/e3 a month ago and switched cop's w/GMS...
problem started Friday...pulled all GMS cop'f off and re-installed factory cop's
over the same spark plug it came from...same problem!!!
checked all cop bolts...checked all connections...cleared all old codes...
only dove it for about 10 minutes and code P 0358 came up...
is that the #8 (drivers/rear) cylinder misfire???
I need to drive more for more codes...do I need to check plugs too???
#42
#44
#45
What do you mean "IF"? You have some reason to doubt that I'm doing what I said? Not sure how to take your comments but it's not coming across very well.