after 20 to 30 miles my truck picks up a bad miss at lowend and overdrivw on 1999 Ford F-150

missig bad after 20 miles or so a small miss otherwise only code evap leak but has been there before miss started

by in Burnsville, NC on November 15, 2013
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3 answers
ANSWER by , November 15, 2013
poss alot of things do you have any eng codes?
ANSWER by , November 15, 2013
Also you can have a cylinder contribution test performed with a scanner, most likely an ignition coil or coils failing.
ANSWER by , November 16, 2013
From the description it sounds like you have a type-a ignition misfire, the threshold for setting dtcs on older fords is broader so they won't set a code as fast as a newer ford. You'll need to take it to a shop that has a power balance test capability that will show exactly which cylinder is misfiring to get an accurate diag.