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IMO - one of the many great things about a V-8 is its ability to idle smoothly. With only 1500 miles, suggest to have a conversation with the dealer - certainly not a widespread problem I've heard of with the 4.6L.
1989 F150 XLT standard-cab shortbed 4x4, 5.0L, AOD, 3.55 gears, manual hubs, 31x10.50 tires, 218K miles. Repainted Oct09. SOLD - Jan2015
2014 F150 XLT standard-cab shortbed 4x4, 5.0L, 6-speed auto, 3.55 gears, auto hubs, locking diff, trailer pkg, 5K miles.