la_leo

2011 f150 5.0 new motorcraft plugs gapped at .045. This truck seems to run well, but at idle I can feel a slight rough idle. It's constant, but no check engine light. If I give it some throttle and hold it, especially at 1000 to 3000 rpms, it's very noticeable. Do all the 5.0s run like this? It's perfect driving on the road and in town driving, no shutters or stalls. It's more irritating than anything.

gDMJoe

la_leo

Interesting....I was under the impression .045 was correct

BlueBeast13

Ford changed the plug gap spec on the 12's and newer. Ford called for a gap of .041-.047 on the 2011. I don't know if it has ever been discussed as to why they changed the recommend plug gap. I have read some posts on here about the subject where some peoples have gapped their plugs down to .045 and claimed slightly better idle and smoother 6th gear cruise acceleration.

tritonblue

My 2012 with 67k miles does it too. I changed the plugs at 50k and it made no difference. Dealer says it's normal.

F150XTR

Don't the factory spec iridium plugs come pre-gapped? Thought it messes up the fine-wire electrode to try and gap them. Am I wrong?

Manuellabour247

I never trust pregapped plugs. I always double check with a gauge before I install.

MGD

^^^ This. IR's are gappable - just requires a modicum of care, is all.

MGD

mechanicboy

To answer the question as it it running what the OP called rough, well yea, it kind of is normal. If by rough you main slightly uneven idle at certain rpms it's because of the old flathead v8 firing order they used, this is also what helps gives the 5.0 V8 it's very distinctive exhaust note that so many love.

If the engine is shaking violently, then you have something out of balance or uneven compression or some other problem.

Yes, you are wrong, assuming you gap them correctly. Always adjust the ground electrode and never pry against the center electrode. Check out this video:

Straight Shooter

To answer your question no not all 5.0 have a rough idle. My 2014 5.0 with 15,250 miles on it has been smooth since the day I bought it last april.