Forum / Engine & Performance / 2015 Ford F-150 5.0L rough idle at stoplights
Started by Pete Navarro · Sep 29, 2026 9:21 AM · 16 views
· Sep 29, 2026 9:21 AM
My 2015 F-150 with the 5.0L has about 112k miles and lately it idles rough at stoplights. You can feel the whole truck shaking a little, but once I give it gas it smooths right out. No check engine light. Spark plugs were done around 80k. Where should I start looking?
Certified Mechanic · Sep 29, 2026 5:24 PM
Start with the air side, not the ignition side. Your plugs were done at 80k and Ford calls for them at 100k on this truck, so with only 32k on the set, ignition is not where I would start.
On the 2015 5.0L, a rough idle that smooths out under throttle with no check engine light almost always comes down to three things.
First, a dirty throttle body. Carbon builds up around the blade and the computer loses its fine control of airflow at idle. Pop the intake tube off: if the bore is black around the blade, clean it with throttle body cleaner and run an idle relearn afterward. This is the single most common cause of exactly your symptoms on the Coyote.
Second, a vacuum leak, and on this engine the PCV hose assembly is a known failure point. Unmetered air leans out the mixture right where it matters most, at idle. Check fuel trims with a scanner: positive at idle that normalize under load means a leak.
Third, and do not skip this one: engine mounts. If the whole truck shakes but the tach needle sits steady, the engine may be running fine and the mounts are just transmitting every pulse into the frame. Test it at the next light: shift to Neutral. If the shake fades, suspect mounts, not misfire.
My bet is the throttle body. It is the cheapest fix, a driveway job, and it matches your symptoms better than anything else on this engine.