Sounds like the idle air control motor is acting up. That may be the idle fluctuation.
As far as the jerking, how old are the plugs? Make sure there is no coolant in the tubes for the plugs as it indicates a bad intake manifold.
I am assuming a 4.6 v8 since you provided no engine size
Roy
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Sunday, January 6th, 2013 AT 2:58 PM