I am hoping that you guys can help remove my confusion.

I have a 2005 5.4L 4x4 with 170,000 miles and am having an issue with a rough idle when engine is below operating temp. There is also a hesitation and lack of power until the engine heats up a bit. This is not 100% of the time. The engine also randomly idles at 1300-1500 rpm before settling down and sometimes only 900-1000. There is also a bid of a smell initially from the exhaust.

It also exhibits an issue where it runs perfectly fine when at normal operating temp for the most part. The issue comes up when I am running at highway speed and go to pass someone. If the trans drops down and I keep my food in it, it will start to lose power and eventually start bucking a little. The CEL starts blinking and there is a loss of power for a short time. After 30 seconds or so, it is back to running normally unless I put it under that load again. This is when it generates the misfire code P0306.

The plugs have around 12,000 miles on them and I used anti-seize (which I have since read was not necessary). The COPs are probably original. Should they be replaced as a set or just troubleshoot one at a time?

Where would be the best place to start troubleshooting this?

 

Antiseize is mandatory on the 3 valve with 2 piece plugs - it must be high temperature nickel and used on the ground barrel.

 

I did it right then. I appreciate you letting me know.

 

Is the CEL (check engine light) coming on or blinking?

 

The CEL blinks and then stores the code but the light goes out.

 

Swap #6 coil with another one, clear the codes, and see if the miss changes cylinders. If it does, replace the one coil. If not, pull #6 plug and look for damage.

 

I will try that and see what happens. Thank you for the guidance.

 

After swapping the coils, the problem followed so I replaced the coil. Once I did that, the problems went away. I really appreciate the guidance.

 

Glad you got it fixed. You had some great assistance and thanks for letting us know what the fix was.

 

Hello. I was reading this post because I have had a similar issue with slightly different results. Mine code was an cylinder 7 misfire. I have 170000 miles, new COP on all 8 November of 2015. Plugs were changed at 108000. Truck is a 2004 5.4L. I had the same chugging under load after warmed up, cold seemed to run ok. When warm engine idles under 1000 rpm. Easy driving went well until needed more power then chugging began and eventually the engine light came on. I swapped 7 with 5 and after short drive went back and still showed 7 misfire. Tech at OReilleys said drive longer. I was low on gas so I put some Lucas injector cleaner and 10 gallons of gas in to keep it pretty concentrated. 5 miles or so light went out. Seemed to smooth out. CEL has not come back on but it still chugs under load, not as bad as previously. If I stay in park and slowly rev engine I can't get a steady rpm until around 1500, it surges. A few times now it has been slow to respond to throttle then will surge up. Thoughts??

 

Sounds like you have a bad injector. I would swap injectors and see if the misfire goes with the #7 injector. I'd also put a couple bottles of Gumout for high mileage engines in a tank of gas.

 

This really sounds like what my truck used to do...it resulted in the replacement of the passenger side head, catalyitic converter and phaser, and miscellaneous parts around 81K miles...they also replaced the fuel injector on cylinder #3...about $8k in work under warranty...

I really thought it was probably the injector that caused the whole mess...the dealer refused to run it through the customer satisfaction program for the fuel injectors because they couldn't prove that it was the cause...so it was covered under the extended warranty with a $ 100 deductable...

 

i am going to run more injector cleaner. I was surprised at the results of first treatment. I had thought about moving injector but had not had the time yet. Thanks.

 

[SPOILER][/SPOILER

I am way out of warranty so I am hoping I can get by on just injectors if needed. Thanks

 

Instead of running Lucas, use Techron. That's the best and is the only fuel additive "approved" by Ford.