Tunnel_Rat

Truck feels like it is misfiring when it is cold, any suggestions on where to start looking. Thanks

2005 F-150 FX4 5.4L

gforceman

Same issue here and a rough idle gonna change my plugs even tho there 8 months old... and 1 was damaged due to water in plug well after running through water on road.

painthorseowner

How many miles, and have the plugs ever been changed? The plugs and/or coil packs are the most likely culprit.

C Dawg222

Does anyone know if an exhaust manifold leak would cause a rough idle/misfire feeling when at idle?

Pretty sure that's what I'm hearing when accelerating from cold with windows down.

Sorry OP...not trying to hi-jack your thread or anything.

McLubben

Pardon my ignorance, what is a "misfire" anyways and how would you know if you had one?

painthorseowner

Misfire means that for whatever reason, one or more sparkplugs are not firing and igniting the fuel vapor in the combustion chamber properly. You'll know it because your truck will run roughly, not have normal power driving, and usually cause a check engine light if it's a steady misfire. Often though it starts as a random misfire, meaning it(bad plug or coil pack) will fire most of the time but occasionally miss a few cycles, this may NOT cause a check engine light, but will be felt by the driver.

Tunnel_Rat

I have 140k miles on the truck, plugs were changed at 120k, the misfire is only when the vehicle is cold, in gear and at idle once I step on the gas there is very little lag and then the truck runs fine. Once the truck warms up the misfire goes away. Also if the truck is idling but in park it does not do it.

greenf1502007

I'm also experiencing the same thing. 4.6 with 78,000 miles

curtk69

could be fuel injectors, coil on plug, spark plug, dirty maf sensor, dirty throttle body, worn phasers, possibly bad o2 sensors,

gforceman

Bad 02 sensors can cause a rough idle? Even the no cell I had a 0430 a couple of weeks ago did relplace injextors and 2 plugs on that bank no light still rough idle like 1 cyl isnt workibg right I have a reader but can't read live data.. have 150 k. On the original ones. . All other possibilities posted above where done. Except 02 sensors gonna replace rest of plugs and cops .. no intention to hijack thread