PIMPIN F150

i have a 4.6L engine has some sort of misfire its not a complete dead cylinder. the misfire usually happens when engine reaches its normal temp and im at a stop light. it would start to shake a little bad but after like 30 seconds it will even out and run fine. i can rev the engine during this and it will go away but only seems to miss on idle.

BlueSmoke

I don't know dude. Mine started doing this last year but it wouldn't clear up when giving it gas. It would get way worse and SES light would start blinking. Trouble codes read a misfire in cylinder 1 and 8. Had the plugs and wires changed (1998) and it still does it. A friend that works for Ford told me it was probably the coils but those are on opposite coils and no other cylinder misfires. I've lived with it but it's annoying.

Warspite

Misfires can get masked at higher RPM - it would show up at idle or at a stop light. Most here simply replace the coil pack or just the plug (code reader would pick up which cylinder it is). Just fixed a 2006 Crown Vic with a new coil on plug (~$100).

scbf150

i have an 01 f150 and i had a similar situation that ended up being the coil. Mine has cop, and the truck ran perfect when the engine was cold but once it warmed up it would start shuttering (a lot worse in od). It eventually threw a code for misfire on #7. At first i only changed the sparkplug because the coil resistance read the same as a new one. Truck ran good for about a day and then symptoms returned. Changed the coil and that fixed it. As the temp goes up so does the resistance, i think thats why my coil was acting the way it was. Good luck.

mpbball2332

pretty old post but you guys figure it out? it just happened to me 98 4.6. just changed plugs about 2 weeks ago

Frank_Ford

First find out what cylinder is misfiring and then check the plug, clean out the plug socket for dirt and oil, reinstall the plug or new plug, and put a little di electric grease in the plug wire connection. If you find it is the number 4 plug in the back passenger side, you may have a leak from your heater hose that is going down the plug socket. The water turns to steam and shorts out your connection and causing the misfire. See if you can feel any water where the heater hose connects to the heater core. If leaking, you may need to replace heater hoses. Also, if your plug continue to work loose, you can try a little thread locker on them. Not something I like to do but with a 98 truck, it should last you for a few years. As long as the engine is hot, you can still get the plugs out should you need to in the future.