Bought a 2013 platinum 5.0 at 76K.
It always had a noticeable idle but I read that was common of the 5.0.

Oil changes every 5k with Mobil synthetic. At 100k I did new motor craft plugs.
Never needed anything other than that until 120k

At 120k I noticed the idle getting worse. Took it to Ford, they said sometimes heads have issues with carbon and wanted to run a fuel and intake “treatment” through it. Seemed like bull**** to me but it’s wife’s truck, needed it back quick etc. So they did it. Idle seemed to improve. Then it started throwing cylinder 5 misfire codes.

I replaced coil pack 5. Plug looked fine. Problem didn’t resolve. Swapped coils around. Misfire stayed in cylinder 5. Idle slowly got worse, misfire codes slowly became more common.

Then I started noticing the misfire codes and rough idle improved right after a fresh oil change. So I experimented with oil. Found it runs best on motor craft 5-20 and a quart of marvel.

Also during this issue the truck started having hard starts after refueling. I replaced the evap solenoid and so far that seems to have solved it.

my next plan is to compression test and leak down test cylinder 5. But, that doesn’t explain the improvement on oil changes unless I’m missing something.

Has anyone else had this problem and solved it? Thanks

 

Do you have access to E85? I have the same year and engine and when i run that you can't tell the engine is running at idle.

 

I am guessing yes. I live in Oklahoma City. I’ll try that. You had a misfire as well and e85 cleared it up?

 

No miss fire just the typical 5.0 idle. Be sure to wait until your tank is almost empty before filling it.

 

The fuel and intake treatment should not have been done for a 2013 as it’s port fuel injection. I’d check and possibly reclean the Maf and intake sensor as they probably knocked something loose. In addition, you might try a Techron gas additive to burn whatever carbon they may have knocked loose. Those cleanings are huge money makers for dealers as they usually cause more harm than good to a well running engine. If it was a eb with di then those would be advised in some cases.

 

I dont understand a rough idle. Granted, my 5.0 is a 2017, and my 5.0 idles so smoothly that you cant feel it idling.
now I have a 2013 with a 6.2, and it idles smoothly as well, but not like the 17 5.0.
I would do a compression check and definitely do a leak down .